Articles including natural biodegradable polysaccharides and uses thereof

ABSTRACT

Medical articles having a body member including natural biodegradable polysaccharides are described. The body member is formed from a plurality of natural biodegradable polysaccharides having pendent coupling groups. The body member can also include a bioactive agent which can be released to provide a therapeutic effect to a patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present non-provisional Application claims the benefit of commonlyowned provisional Application having Ser. No. 60/719,466, filed on Sep.21, 2005, and entitled ARTICLES AND COATINGS INCLUDING NATURALBIODEGRADABLE POLYSACCHARIDES AND USES THEREOF.

TECHNICAL FIELD

The present invention relates to medical articles comprising a naturalbiodegradable polymeric material. Bioactive agents can be included inthe medical articles to provide a therapeutic effect to a patient.

BACKGROUND

Recently, the use of drug-eluting stents (DES) in percutaneous coronaryinterventions has received much attention. DES are medical devices thatpresent or release bioactive agent into their surroundings (for example,luminal walls of coronary arteries). Generally speaking, a bioactiveagent can be coupled to the surface of a medical device by surfacemodification, embedded, and released from within polymeric materials(matrix-type), or surrounded by and released through a carrier(reservoir-type). The polymeric materials in such applications shouldoptimally act as a biologically inert barrier and not induce furtherinflammation within the body. However, the molecular weight, porosity ofthe polymer, a greater percentage of coating exposed on the medicaldevice, and the thickness of the polymer coating can contribute toadverse reactions to the medical device.

Another way to deliver bioactive agents from the surface of a medicaldevice is by using a coating that has a biodegradable polymer, such aspolylactic acid. As the coating degrades, the bioactive agent isreleased from the surface of the device. Although biodegradable coatingsthat include polylactic acid have been described in a number ofdocuments, for example, U.S. Pat. No. 6,258,121, there remains a needfor improved coatings and coating materials.

Some concerns exist that regard the use of biodegradable materials thatdegrade into materials that are not typically found in the body, or thatare found at particularly low levels in the body. These types ofbiodegradable materials have the potential to degrade into products thatcause unwanted side effects in the body by virtue of their presence orconcentration in vivo. These unwanted side effects can include immunereactions, toxic buildup of the degradation products in the liver, orthe initiation or provocation of other adverse effects on cells ortissue in the body.

Another problem is that preparations of some biodegradable materials maynot be obtained at consistent purity due to variations inherent innatural materials. This is relevant at least with regard tobiodegradable materials derived from animal sources. Inconsistencies inpreparations of biodegradable materials can result in problematiccoatings.

It is also desirable to provide biodegradable drug delivery coatingsthat are easy to prepare, cost effective, and that also offer a widerange of flexibility with regard to the type and amount of drug or drugsto be delivered from the biodegradable coating.

Other aspects of the present invention relate to the use of polymericcoatings for providing a sealant function to medical articles.Biodegradable sealant compositions have been used on articles havingporous surfaces, such as fabrics associated with implantable medicalarticles. The sealant coating initially renders the porous surfaceimpermeable to fluids for a period of time. However, as the sealantmaterials degrade and are resorbed by the body, cells involved in tissuerepair infiltrate the porous material and replace the sealant materials.Thus, newly formed tissue replaces the original function of the coatedsealant over a period of time.

Animal-derived sealant materials such as collagen and gelatin arecommonly used to coat textile grafts. These materials can be resorbed invivo. The blood clotting protein fibrin has also been utilized as asealant material. Despite their uses, there are drawbacks and concernswith using these types of sealant materials. One particular problem isthat it is difficult to produce consistent sealant compositions fromthese animal sources due to batch-to-batch variations inherent in theirproduction.

In many cases the collagen used in sealant technologies is obtained fromnon-human animal sources, such as bovine sources. In these cases thereis the possibility that bovine collagen preparations may containunwanted contaminants that are undesirable for introduction into a humansubject. One example of an unwanted contaminant is the prionic particlesthat cause Bovine Spongiform Encephalopathy (BSE).

BSE, also termed Mad Cow Disease, is one of a group of progressiveneurological diseases called transmissible spongiform encephalopathies,or TSEs (named for deteriorated areas of the brain that look likesponges). Various forms of TSE have been reported, including scrapie insheep and chronic wasting disease in elk and mule deer. It is generallybelieved that the use of recycled animal parts led to the cross-speciescontamination of scrapie in sheep to mad cow disease, and the ingestionof contaminated beef and bovine products led to the human variant ofthis disease, Creutzfeldt-Jakob Disease (CJD).

Additional concerns are that preparations from animal sources mayprovide other unwanted contaminants, such as antigenic factors. Theseantigenic factors may promote a localized immune response in thevicinity of the implanted article and foul its function. These factorsmay also cause infection as well as local inflammation.

While synthetic materials can be used in the preparation of sealantcompositions, these synthetic materials have the potential of degradinginto non-naturally occurring products. These non-naturally occurringproducts have the potential to be at least partially toxic to theorganism or immunogenic and cause inflammation, as well as infection, ator around the site of implantation.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides compositions and methodsfor preparing biodegradable coatings that are particularly useful forcoating surfaces of implantable medical devices, such as stents andcatheters, and are capable of releasing bioactive agents from the devicesurface. These coating compositions include a natural biodegradablepolysaccharide as a component that can be crosslinked to form a matrixfrom which a therapeutic material such as a drug, a biomolecule, orcells (referred to herein as a “bioactive agents”) can be released orretained. In some embodiments of the invention, a bioactive agent ispresent in and can be released from the biodegradable matrix; in otherembodiments a bioactive agent is present in a biodegradablemicroparticle, the microparticle being immobilized within the matrix.

In other aspects of the invention, the natural biodegradablepolysaccharide is used to prepare an article, such as an article thatcan be implanted or formed within the body (for example, by in situformation). In some aspects, the article can be amorphous, such as apolymerized mass of natural biodegradable polysaccharides that is formedwithin or on a portion of the body, by using an in vivo matrix-formingcomposition.

In other aspects, the invention provides an article fabricated fromnatural biodegradable polysaccharide, wherein the article has a definedstructure, and wherein the article can be implanted in the body (such asa filament). Such articles are referred to herein as “medical implants”.A medical implants having a defined structure can be formed by anysuitable process, including molding, extruding, shaping, cutting,casting, and the like.

The article can be used for one or more purposes, such as for releasingor retaining a bioactive agent at a location in the body. For example,the article can be a bioactive agent-containing medical implant ordepot. The article can also provide one or more mechanical or physicalproperties to a portion the body. For example, the natural biodegradablepolysaccharides can be included in a composition used for the formationof a biodegradable medical device such as a stent.

In some aspects, the article, such as an in vivo formed matrix, is usedin methods for the treatment of any one or more of a variety of medicalconditions or indications, including restoring, improving, and/oraugmenting tissue growth or function, in particular those fororthopedic, dental, and bone graft applications. These functions can beprovided by placing a polymerized matrix of biodegradablepolysaccharides in contact with a host tissue. The matrix can restore orimprove tissue growth or function by, for example, promoting orpermitting formation of new tissue between and into the matrix. Theeffect on tissue can be caused by the biodegradable polysaccharideitself, or the biodegradable polysaccharide in combination with one ormore bioactive agent(s) that can be present in and/or released from thematrix. Exemplary bioactive agents that can affect tissue functioninclude peptides, such as peptides that are involved in tissue repairprocesses and belonging to the EGF, FGF, PDGF, TGF-β, VEGF, PD-ECGF orIGF families, and also peptides derived from bone morphogenetic protein2, or BMP-2. The bioactive agent can also be a cell, such as a platelet.

In some aspects, the coating or article can include a radiopacifyingagent.

In preparing the coatings or articles, a plurality of naturalbiodegradable polysaccharides are crosslinked to each other via couplinggroups that are pendent from the natural biodegradable polysaccharide(i.e., one or more coupling groups are chemically bonded to thepolysaccharide). In some aspects, the coupling group on the naturalbiodegradable polysaccharide is a polymerizable group. In a free radicalpolymerization reaction the polymerizable group can crosslink naturalbiodegradable polysaccharides together in the composition, therebyforming a natural biodegradable polysaccharide matrix, which can be aportion of a coating, an in-vivo formed matrix, or the body member of amedical implant.

The natural biodegradable polysaccharides described herein arenon-synthetic polysaccharides that can be associated with each other toform a matrix, which can be used as a coating or as an article, forexample, a medical implant or an in-vivo formed matrix. The naturalbiodegradable polysaccharides can also be enzymatically degraded, butoffer the advantage of being generally non-enzymatically hydrolyticallystable. This is particularly advantageous for bioactive agent delivery,as in some aspects the invention provides coatings or articles capableof releasing the bioactive agent under conditions of enzyme-mediateddegradation, but not by diffusion. Therefore, the kinetics of bioactiveagent release from the coatings or articles of the invention arefundamentally different than those of coatings prepared from syntheticbiodegradable materials, such as poly(lactides).

Natural biodegradable polysaccharides include polysaccharide and/orpolysaccharide derivatives that are obtained from natural sources, suchas plants or animals. Exemplary natural biodegradable polysaccharidesinclude amylose, maltodextrin, amylopectin, starch, dextran, hyaluronicacid, heparin, chondroitin sulfate, dermatan sulfate, heparan sulfate,keratan sulfate, dextran sulfate, pentosan polysulfate, and chitosan.Preferred polysaccharides are low molecular weight polymers that havelittle or no branching, such as those that are derived from and/or foundin starch preparations, for example, amylose and maltodextrin.

Because of the particular utility of the amylose and maltodextrinpolymers, in some aspects natural biodegradable polysaccharides are usedthat have an average molecular weight of 500,000 Da or less, 250,000 Daor less, 100,000 Da or less, or 50,000 Da or less. In some aspects thenatural biodegradable polysaccharides have an average molecular weightof 500 Da or greater. In some aspects the natural biodegradablepolysaccharides have an average molecular weight in the range of about1000 Da to about 10,000 Da. Natural biodegradable polysaccharides ofparticular molecular weights can be obtained commercially or can beprepared, for example, by acid hydrolysis and/or enzymatic degradationof a natural biodegradable polysaccharide preparation, such as starch.The decision of using natural biodegradable polysaccharides of aparticular size range may depend on factors such as the physicalcharacteristics of the coating composition (e.g., viscosity), thedesired rate of degradation of the coating, the presence of otheroptional moieties in the coating composition (for example, bioactiveagents, etc.), etc.

The natural biodegradable polysaccharides that are used in accordancewith the methods and compositions of the invention are readily availableat a low cost and/or can be prepared easily using establishedtechniques. This allows for a cost effective method of coating andfabricating medical articles.

The use of natural biodegradable polysaccharides, such as maltodextrinor amylose, provides many advantages when used in a coating compositionapplied to the surface of a medical device, or for the formation of anarticle, such as one that can be used in vivo. Degradation of a naturalbiodegradable polysaccharide-containing article, or coating from thesurface of a medical device, can result in the release of, for example,naturally occurring mono- or disaccharides, such as glucose, which arecommon serum components. Furthermore, the use of natural biodegradablepolysaccharides that degrade into common serum components, such asglucose, can be viewed as more acceptable than the use of syntheticbiodegradable polysaccharides that degrade into non-natural compounds,or compounds that are found at very low concentrations in the body.

In some aspects of the invention, this advantageous feature is reflectedin the use of natural biodegradable polysaccharides which are non-animalderived, such as amylose and maltodextrin, and that degrade intoproducts that present little or no immunogenic or toxic risk to theindividual. The invention provides improved, cost-efficient, naturalbiodegradable polysaccharide compositions for articles or coatings thatcan be used in a variety of medical treatments.

Another advantage of the invention is that the natural biodegradablepolysaccharide-based coatings are more resistant to hydrolyticdegradation than other biodegradable polymers, such as poly(lactides).Degradation of the natural biodegradable polysaccharides of theinvention are primarily enzyme-mediated, with minimal or no hydrolysisof the natural biodegradable polysaccharide occurring when a naturalbiodegradable polysaccharide-containing coating is prepared underambient conditions. This allows the natural biodegradablepolysaccharide-based coatings to remain substantially stable (forexample, resistant to degradation) prior to placing the coated-articlein vivo. For example, a natural biodegradable polysaccharide coatedarticle can be manipulated in a non-biological, aqueous-based-mediumwithout risk that the coating will prematurely degrade due tonon-enzyme-mediated hydrolysis. Other coatings that are based onbiodegradable polymers such as poly(lactide) orpoly(lactide-co-glycolide) are subject to hydrolysis even at relativelyneutral pH ranges (e.g., pH 6.5 to 7.5) and therefore do not offer thisadvantage.

Therefore, the invention includes natural biodegradablepolysaccharide-containing compositions, coatings, articles, and methodsof preparing such that have the advantage of providing stability in thepresence of an aqueous environment.

In one aspect, the invention provides a shelf-stable composition forpreparing a biodegradable coating, the shelf stable compositioncomprising a natural biodegradable polysaccharide comprising couplinggroups. These compositions could be obtained or prepared, according tothe details provided herein, and then stored for a period of time beforethe composition is used to form a biodegradable coating or article,without significant degradation of the natural biodegradablepolysaccharide occurring during storage. Accordingly, the invention alsoprovides methods for preparing a biodegradable coating comprisingpreparing a biodegradable coating composition comprising a naturalbiodegradable polysaccharide comprising coupling group; storing thecoating composition for an amount of time; and then using the coatingcomposition to prepare a biodegradable coating or a biodegradablearticle. In some aspects, the biodegradable article is formed in situ,for example, by promoting the polymerization of the naturalbiodegradable polysaccharide within the body. Optionally, one or morebioactive agents and/or microparticles can be added before or afterstorage of the coating composition.

In a related aspect, the invention also provides the advantage of beingable to perform methods wherein the natural biodegradable polysaccharideis subject to exposure to an aqueous solution without riskingsignificant degradation of the natural biodegradable polysaccharide. Forexample, the natural biodegradable polysaccharide may be contacted withan aqueous solution in a synthetic or post-synthetic step, includingaddition synthesis reactions and purification steps, or a coating thatincludes the natural biodegradable polysaccharide can be contacted withan aqueous solution in, for example, a sterilization step or a step thatinvolves incorporation of a bioactive agent into the biodegradablecoating.

In yet another aspect, the invention relates to the stability of anarticle or a coating that is formed on an article. The inventionprovides a method comprising obtaining an article formed from, or havinga coating comprising, a natural biodegradable polysaccharide, and thencontacting the article with an aqueous solution for a period of timewherein the article or coating remains predominantly stable in thesolution. The aqueous solution can be, for example, a storage solution,a solution that is used to hydrate the surface of the coated device, oran aqueous sterilization solution.

Degradation of the natural biodegradable polysaccharide-containingcoating or article may commence when placed in contact with a bodyfluid, which may include natural biodegradable polysaccharide-degradingenzymes, such as carbohydrases.

The invention also provides a useful way to deliver larger hydrophilicbioactive agents, such as polypeptides, nucleic acids, andpolysaccharides, as well as viral particles and cells from thebiodegradable article, or biodegradable coating on a surface, such as amedical device or a coating on a surface thereof. Comparatively, the useof non-degrading drug delivery matrices may not be useful for thedelivery of these larger bioactive agents if they are too large todiffuse out of the matrix. However, according to some aspects of theinvention, an article or a coating that includes a matrix of the naturalbiodegradable polysaccharide having a bioactive agent can be placed orformed in the body, and as the matrix degrades the bioactive agent isgradually released from the matrix. In one aspect of the invention, thebioactive agent has a molecular weight of about 10,000 Da or greater.

In some aspects, the invention provides a drug-releasing biodegradablearticle, coating, or composition comprising (i) a natural biodegradablepolysaccharide, preferably selected from amylose and maltodextrin,comprising an ethylenically unsaturated group, (ii) an initiator, and(iii) a bioactive agent selected from the group of polypeptides,polynucleotides, and polysaccharides.

In another aspect, a coated surface is prepared on a medical device,such as a stent or catheter. The methods include disposing in one ormore steps the following reagents on a surface: (a) an initiator, (b) anatural biodegradable polysaccharide, preferably selected from amyloseand maltodextrin, comprising an ethylenically unsaturated group, and (c)a bioactive agent. After the components have been disposed on thesurface, the initiator is activated to crosslink a plurality of naturalbiodegradable polysaccharides comprising ethylenically unsaturatedgroups that are present in the composition, thereby forming a coating onthe surface that includes the bioactive agent.

Depending on the application, the initiator can be first disposed on thesurface, followed by disposing the natural biodegradable polysaccharideand bioactive agent on the layer of initiator. Alternatively, theinitiator, natural biodegradable polysaccharide, and bioactive agent aremixed and disposed together on the surface.

Therefore, in some aspects, the invention provides a method for deliveryof a bioactive agent, or more than one bioactive agent, to a subject.The method comprises the steps of providing a coated article to asubject, the coated article having a biodegradable coating whichcomprises a plurality of natural biodegradable polysaccharidesassociated via coupling groups, and bioactive agent. The coated articleis then exposed to a carbohydrase to promote the degradation of thecoating and release of the bioactive agent. For example, a biodegradablecoating or article including amylose and/or maltodextrin polymers can beexposed to an α-amylase to promote degradation of the coating andrelease of the bioactive agent. The step of exposing can be performed byplacing the biodegradable coating or article in a patient. In theabsence of the carbohydrase there is substantially no release of thebioactive agent. In some aspects the bioactive agent comprises apolypeptide, such as an antibody or an antibody fragment.

In some aspects, the methods of the invention can be used to preparecoatings wherein an amount of bioactive agent in the range of 1% to 17%of the total amount of bioactive agent present in the coating isreleased from the coating within a period of 2 days, and coatingswherein an amount of bioactive agent in the range of 1% to 20% of thetotal amount of bioactive agent present in the coating is released fromthe coating within a period of 8 days.

In other aspects, the bioactive agent is delivered from a medicalimplant having a biodegradable body member which comprises a pluralityof natural biodegradable polysaccharide associated via pendent couplinggroups, the body member also including a bioactive agent. The medicalimplant is then exposed to a carbohydrase to promote the degradation ofthe implant and release of the bioactive agent.

In some aspects, the methods of the invention can be used to preparemedical implants wherein an amount of bioactive agent in the range of 1%to 17% of the total amount of bioactive agent present in the medicalimplant is released within a period of 8 days, medical implants whereinan amount of bioactive agent in the range of 1% to 41% of the totalamount of bioactive agent present in the medical implant is releasedwithin a period of 14 days, and medical implants wherein an amount ofbioactive agent in the range of 1% to 60% of the total amount ofbioactive agent present in the medical implant is released within aperiod of 21 days.

Alternatively a carbohydrase can be administered to a subject, or thecarbohydrase can be provided to a portion of the article, wherein thecarbohydrase is released from the portion and locally causes thedegradation of the coating.

The coatings can also have favorable bioactive agent-releasingproperties when the coated article has been placed in the body. In thisregard, the present invention provides an overall improvement in termsof providing coatings for implantable medical articles. Articles thatare fabricated from the biodegradable polysaccharides can have many ofthe same beneficial surface characteristics as provided by thebiodegradable polysaccharide coatings.

In another aspect of the invention, the natural biodegradablepolysaccharide is modified with a hydrophobic moiety in order to providea biodegradable matrix having hydrophobic properties. Therefore, abiodegradable coating or article can be formed from naturalbiodegradable polysaccharide comprising one or more pendent couplinggroups and one or more pendent hydrophobic moieties. Exemplaryhydrophobic moieties include fatty acids and derivatives thereof, andC₂-C₁₈ alkyl chains.

Therefore, in some aspects of the invention, modification of the naturalbiodegradable polysaccharide allows for preparation of coatings orarticles that are biodegradable and that can release a hydrophobicbioactive agent.

In other aspects, the hydrophobic moiety pendent from the naturalbiodegradable has properties of a bioactive agent. Upon degradation ofthe matrix, the hydrophobic moiety can be hydrolyzed from the naturalbiodegradable polymer and released to provide a therapeutic effect. Oneexample of a therapeutically useful hydrophobic moiety is butyric acid.

In yet another aspect, the invention provides methods and articles forimproving the stability of a bioactive agent that is delivered from acoating or an article by utilizing a natural biodegradable non-reducingpolysaccharide. The non-reducing polysaccharide can provide an inertmatrix and thereby improve the stability of sensitive bioactive agents,such as proteins and enzymes. The article or coating can include amatrix having a plurality of natural biodegradable non-reducingpolysaccharides along with a bioactive agent, such as a polypeptide. Anexemplary non-reducing polysaccharide comprises polyalditol.Biodegradable non-reducing polysaccharides can very useful forformulating coatings or articles that release the bioactive agent over aprolonged period of time.

While it is desirable to make coatings or articles that provide desiredproperties (for example, bioactive agent release, wettability, etc.),their actual preparation can be challenging. In particular, the use ofsome polysaccharides for preparing coatings or articles may result inproducts that are unsuitable for use. For example, somepolysaccharide-based coatings, including those made from starch-basedmaterials, have the potential to be overly brittle and inflexible. Whilethese properties may be suitable for pharmaceutical capsules or tabletsthey are generally undesirable as properties for coatings or articles,such as bioactive agent releasing or sealant coatings, or medicalimplants.

Despite this, the present invention demonstrates the preparation ofarticles and coatings that include natural biodegradable polysaccharidesthat are suitable for in vivo use. These products display excellentphysical characteristics and are suitable for use in applicationswherein a particular function, such as bioactive agent delivery or asealant function is desired. For example, coatings or articles can beprepared having viscoelastic properties. In one aspect of the invention,the coating or article has an elastic modulus value in the range of 27kPa to 30 kPa.

The coatings of the present invention can have desirable surfaceproperties that include elasticity and wettability, in addition to beingbiodegradable. Also, it has surprisingly been discovered that thecoatings demonstrate excellent lubricity, which can provide distinctadvantages for short term and single use devices. Therefore, in oneaspect, the invention presents a method for providing lubricity to anarticle surface comprising the steps of disposing a compositioncomprising a plurality of natural biodegradable polysaccharidescomprising pendent coupling groups and activating the coupling groups topromote association of the plurality of natural biodegradablepolysaccharides and formation of a lubricious coating on the articlesurface.

The coatings can be formed on the surfaces of medical articles,including those designed for single use or for short-term use. Forexample, a lubricious coating can be formed on a catheter.

Coatings including natural biodegradable polysaccharides can be preparedto provide a lubricity of 20 g or less, and can also be prepared toprovide a lubricity of 15 g or less, or 10 g or less, as based onfriction testing. The coatings were also shown to be highly durable, aslubricity was maintained during multiple cycles of friction testing.Methods utilizing a photoinitiator have been shown to provide coatingswith both excellent lubricity and durability.

In some embodiments of the invention, the methods of preparing thecompositions for fabrication of articles and/or coated surfaces do notrequire the use of organic solvents. The use of organic solvents can bephysically hazardous. Use of organic solvents can potentially destroythe activity of a bioactive agent that can be optionally included in thenatural biodegradable polysaccharide-based composition.

Many of the advantageous features of the present natural biodegradablepolysaccharide-containing coatings and articles are thought to beprovided by the starting materials, in particular the naturalbiodegradable polysaccharides having pendent coupling groups. In someaspects the natural biodegradable polysaccharides have pendentpolymerizable groups, such as ethylenically unsaturated groups. In apreferred aspect, the degradable polymerizable polymers (macromers) areformed by reacting a natural biodegradable polysaccharide with acompound comprising an ethylenically unsaturated group. For example, insome cases, a natural biodegradable polysaccharide is reacted with acompound including an ethylenically unsaturated group and an isocyanategroup. In another example of synthesis, a natural biodegradablepolysaccharide is treated with an oxidizing agent to form a reactivealdehyde species on the polysaccharide and then reacted with a compoundcomprising an ethylenically unsaturated group and an amine group.Polysaccharide macromers were shown to have excellent matrix formingcapabilities.

Synthesis can be carried out to provide the natural biodegradablepolysaccharide with a desired quantity of pendent coupling groups. Ithas been found that use of a natural biodegradable polysaccharide havinga predetermined amount of the coupling groups allows for the formationof a coating or an article having desirable physical characteristics(for example, the coatings are not brittle). Therefore, in some aspects,the invention provides natural biodegradable polysaccharides having anamount of pendent coupling groups of about 0.7 μmoles of coupling groupper milligram of natural biodegradable polysaccharide. Preferably theamount of coupling group per natural biodegradable polysaccharide is inthe range of about 0.3 μmoles/mg to about 0.7 μmoles/mg. For example,amylose or maltodextrin can be subject to a synthesis reaction with acompound having an ethylenically unsaturated group to provide an amyloseor maltodextrin macromer having a ethylenically unsaturated group loadlevel in the range of about 0.3 μmoles/mg to about 0.7 μmoles/mg.

In some aspects of the invention an initiator is used to promote theformation of the natural biodegradable polysaccharide matrix for articleor coating formation. The initiator can be an independent compound or apendent chemical group used to activate the coupling group pendent fromthe natural biodegradable polymer and promote coupling of a plurality ofnatural biodegradable polymers. When the coupling group pendent from thenatural biodegradable polysaccharide is a polymerizable group, theinitiator can be used in a free radical polymerization reaction topromote crosslinking of the natural biodegradable polysaccharidestogether in the composition.

Therefore, in one aspect, the invention provides a biodegradable coatingor article composition comprising (i) a natural biodegradablepolysaccharide, preferably selected from amylose and maltodextrin,comprising a coupling group, (ii) an initiator, and (iii) a bioactiveagent, wherein the coupling group is able to be activated by theinitiator and promote crosslinking of a plurality of naturalbiodegradable polysaccharides. In some aspects of the invention theinitiator is independent of the natural biodegradable polysaccharide andin other aspects the initiator is pendent from the natural biodegradablepolysaccharide. Preferably, the natural biodegradable polysaccharidecomprises an ethylenically unsaturated group. In some aspects aphotoinitiator is used, such as a photoinitiator that is activated bylight wavelengths having no or a minimal effect on the bioactive agentpresent in the composition.

In another aspect, the initiator includes an oxidizing agent/reducingagent pair, a “redox pair,” to drive polymerization of the biodegradablepolysaccharide. In preparing the biodegradable coating or article theoxidizing agent and reducing agent are combined in the presence of thebiodegradable polysaccharide. One benefit of using a redox pair is that,when combined, the oxidizing agent and reducing agent can provide aparticularly robust initiation system. This is advantageous as it canpromote the formation of a matrix, for example, useful for coating orarticle preparation, from biodegradable polysaccharide compositionshaving a relatively low viscosity. This can be particularly useful inmany applications, especially when the biodegradable polysaccharidecomposition is used for the formation of an in situ polymerized article.For example, a low viscosity composition can be passed through a smallgauge delivery conduit with relative ease to provide the compositionthat can polymerize in situ.

In some aspects of the invention, the viscosity of the composition isabove about 5 centi Poise (cP), or about 10 cP or greater. In otheraspects of the invention the viscosity of the composition is betweenabout 5 cP or 10 cP and about 700 cP, and in some aspects between about5 cP or 10 cP and about 250 cP. In some aspects the viscosity of thecomposition is above about 5 cP or 10 cP and the biodegradablepolysaccharides in the composition have an average molecular weight of500,000 Da or less, 250,000 Da or less, 100,000 Da or less, or 50,000 Daor less.

A method for preparing a coating or article can include the steps of (a)providing a first composition that includes a natural biodegradablepolysaccharide comprising a coupling group and a first member of a redoxpair (for example, the oxidizing agent) and then (b) mixing the firstcomposition with second composition that includes a second member of theredox pair (for example, the reducing agent). In some aspects the secondcomposition includes a natural biodegradable polysaccharide. Forexample, the first composition can include (a) a natural biodegradablepolysaccharide having a coupling group and an oxidizing agent and thesecond composition can include a (b) natural biodegradablepolysaccharide having a coupling group and a reducing agent. In someaspects, when the first composition is combined with the secondcomposition, the final composition can be about 5 cP or greater.

The oxidizing agent can be selected from inorganic or organic oxidizingagents, including enzymes; the reducing agent can be selected frominorganic or organic reducing agents, including enzymes. Exemplaryoxidizing agents include peroxides, including hydrogen peroxide, metaloxides, and oxidases, such as glucose oxidase. Exemplary reducing agentsinclude salts and derivatives of electropositive elemental metals suchas Li, Na, Mg, Fe, Zn, Al, and reductases. In one aspect, the reducingagent is present in the composition at a concentration of 2.5 mM orgreater when mixed with the oxidizing agent. Other reagents, such asmetal or ammonium salts of persulfate, can be present in the compositionto promote polymerization of the biodegradable polysaccharide.

A coating or article formed using redox polymerization can thereforecomprise a plurality of natural biodegradable polysaccharides associatedvia polymerized groups, a reduced oxidizing agent, and an oxidizedreducing agent. In one preferred aspect, the biodegradable coated layeris formed article having a first coated layer comprising a syntheticpolymer.

The invention also provides alternative methods for preparing a coatedsurface or an article that is biodegradable and that can release abioactive agent. For example, an alternative method for forming acoating includes disposing in two or more steps at least the followingreagents on a surface: (a) a natural biodegradable polysaccharidecomprising a first coupling group, (b) a natural biodegradablepolysaccharide comprising a second coupling group that is reactive withthe first coupling group, and (c) a bioactive agent. According to thismethod reagents (a) and (b) are reactive with each other and aredisposed separately on the surface but can individually include reagent(c). For example, reagent (a) is first disposed on the surface and thena mixture comprising reagent (b) and (c) is then disposed on reagent(a). Reagent (a) reacts with (b) to link the natural biodegradablepolysaccharides together to form a coating that includes reagent (c),the bioactive agent. An article can be formed in a similar manner, forexample, by a method that includes combining (a) a natural biodegradablepolysaccharide comprising a first coupling group with (b) a naturalbiodegradable polysaccharide comprising a second coupling group that isreactive with the first coupling group, and (c) a bioactive agent. Thearticle can be partially or fully formed when reagent (a) reacts with(b) to link the natural biodegradable polysaccharides together to formthe article, which includes reagent (c), the bioactive agent.

In some aspects, the present invention employs the use of biodegradablemicroparticles that include a bioactive agent and a naturalbiodegradable polysaccharide, such as amylose and maltodextrin that havependent coupling groups. The microparticles are used in association withthe natural biodegradable polysaccharides to prepare a biodegradable,bioactive agent-releasing coating for the surface of medical devices.

According to this aspect of the invention, a medical device having acoating that includes a crosslinked matrix of natural biodegradablepolysaccharides and biodegradable microparticles having a bioactiveagent can be placed in the body, and as the biodegradable microparticlesdegrade the bioactive agent is gradually released from the coating.

The natural biodegradable polysaccharide matrix provides the ability toassociate the biodegradable microparticles with the surface of thecoated device. In some arrangements, the biodegradable microparticlesare dispersed in the natural biodegradable polysaccharide matrix. Suchcoatings can be formed by disposing a mixture of (a) biodegradablemicroparticles having a bioactive agent and (b) natural biodegradablepolysaccharides having pendent coupling groups, disposing the mixture ona surface, and then treating the composition to form a coated layerwherein the biodegradable microparticles are dispersed within thematrix.

In other arrangements, the coating is formed by disposing thebiodegradable microparticles independently of the natural biodegradablepolysaccharide having pendent coupling groups. In these arrangements thebiodegradable microparticles can be present predominantly one face ofthe layer that is formed from the natural biodegradable polysaccharideand a microparticle-matrix interface can be formed.

The methods include disposing in one or more steps the followingcomponents on a surface: (a) an initiator, (b) a natural biodegradablepolysaccharide, preferably selected from amylose and maltodextrin,comprising a coupling group, and (c) biodegradable microparticlescomprising a bioactive agent. After the components have been disposed onthe surface, the initiator is activated to couple a plurality of naturalbiodegradable polysaccharide polymers that are present in thecomposition, thereby forming a natural biodegradable polysaccharidematrix on the surface that is associated with the biodegradablemicroparticles having the bioactive agent.

In these aspects, the method includes the steps of (i) disposing acomposition comprising (a) a natural biodegradable polysaccharide havinga coupling group, (b) an initiator, and (c) biodegradable microparticlescomprising a bioactive agent on a surface; and (ii) activating theinitiator to provide a coated composition having the naturalbiodegradable polysaccharide and the biodegradable microparticles havingthe bioactive agent on the surface. Alternatively, the initiator can bedisposed independently of the natural biodegradable polysaccharide.

By including microparticles having a bioactive agent in the naturalbiodegradable polysaccharide-containing coating, the invention alsoprovides a way to effectively and efficiently prepare a variety ofdrug-delivery coatings. The use of microparticles offers the ability toeasily prepare coatings having one or more bioactive agents present indesired amounts in the coating. Such coatings can be prepared byobtaining biodegradable microparticles that have a bioactive agent andthen forming a coating that includes the microspheres associated withthe natural biodegradable polysaccharide matrix. In some aspects,different microparticles having different bioactive agents can beincluded in the coating in desired amounts to provide a bioactiveagent-releasing coating that is able to release a desired combination ofbioactive agents in desired amounts. This is a particular advantage whenusing bioactive agents that are typically not compatible in the samecomposition (for example, bioactive agents that have different physicalproperties).

Microparticles can also be included in articles formed from the naturalbiodegradable polysaccharide. For example, microparticles can beincluded in an implantable medical article formed from the naturalbiodegradable polysaccharides of the invention, or can be included in anarticle that is formed in situ. In these aspects, the presence ofbiodegradable microparticles in articles can offer many of theadvantages that are offered by the presence of the microparticles in thecoatings.

In another aspect, the present invention provides compositions andmethods for preparing sealant materials that are particularly useful inconnection with implantable medical articles having a porous surface,such as grafts, patches, and wound dressings. In preferred aspects, theinventive compositions can be used to prepare a sealant coating forimplantable medical articles, particularly implantable medical articlesthat include a porous surface.

The sealant coating can provide a barrier to the movement of bodyfluids, such as blood, near the surface of the coated article. Forexample, the natural biodegradable polysaccharide-based sealant coatingcan provide hemostasis at the article surface by formation of a tightseal. Gradually, the natural biodegradable polysaccharide in the sealantcoating degrades and a tissue layer is formed as the sealant coating isreplaced by cells and other factors involved in tissue repair. Duringthe process of degradation, natural biodegradable polysaccharidedegradation products, such as naturally occurring mono- ordisaccharides, for example, glucose, are released from the sealantcoating, which can be considered an ideal in vivo degradation productbecause it is commonly found in the body and may also be utilized by thecells involved in tissue repair during the degradation/infiltrationprocess. Gradually, infiltrated tissue growth replaces the function ofthe natural biodegradable polysaccharide-containing sealant coating.

Another particular advantage of the invention is that release of glucosereduces the likelihood that the process of natural biodegradablepolysaccharide degradation and tissue infiltration will promote a stronginflammatory response. This is because the natural biodegradablepolysaccharide-based sealant coating can degrade into materials that arenon-antigenic or that have low antigenicity. Another advantage is thatthe degradation products are free of other materials that may causedisease, such as microbial, viral, or prionic materials potentiallypresent in animal-derived preparations (such as bovine collagenpreparations).

The sealant compositions of the invention, which include naturalbiodegradable polysaccharides, such as amylose or maltodextrin polymers,that can be coupled together to form a matrix (at least a portion of thesealant coating) on the medical article, can include a bioactive agent,which can be released as the sealant coating degrades.

In some aspects, the invention provides a biodegradable sealantcomposition comprising (i) a natural biodegradable polysaccharidecomprising a coupling group, and (ii) an initiator, wherein the couplinggroup is able to be activated by the initiator and promote coupling of aplurality of natural biodegradable polysaccharides. Preferably thenatural biodegradable polysaccharide is a polymer such as amylose ormaltodextrin. In some aspects the sealant composition can also include abioactive agent. The initiator can be independent of the naturalbiodegradable polysaccharide, pendent from the natural biodegradablepolysaccharide polymer, or both pendent and independent of the naturalbiodegradable polysaccharide polymer.

Accordingly, the invention also provides methods for preparing a surfacehaving a sealant coating. The sealant coated surface is prepared on amedical article or article having a porous surface. The methods includedisposing in one or more steps the following reagents on a surface: (a)an initiator, and (b) a natural biodegradable polysaccharide comprisinga coupling group. In some aspects a bioactive agent is also disposed onthe surface. In one preferred aspect, the bioactive agent is aprothrombotic or procoagulant factor. In these aspects, after thecomponents have been disposed on the surface, the initiator is activatedto couple the natural biodegradable polysaccharides that are present inthe composition, thereby forming a natural biodegradable polysaccharidecoating on the surface that includes the bioactive agent.

During the step of activating, the natural biodegradable polysaccharideis contacted with the initiator and the initiator is activated topromote the coupling of two or more natural biodegradablepolysaccharides via their coupling groups. In preferred aspects, thenatural biodegradable polysaccharide includes a polymerizable group,such as an ethylenically unsaturated group, and initiator is capable ofinitiating free radical polymerization of the polymerizable groups.

The invention also provides alternative methods for preparing a sealantcoating on the surface of an article. The methods include disposing atleast the following reagents on a surface: (a) a natural biodegradablepolysaccharide comprising a first coupling group and (b) a naturalbiodegradable polysaccharide comprising a second coupling group, wherein the second coupling group is reactive with the first coupling group.According to this method, reagents (a) and (b) are reactive with eachother to couple the natural biodegradable polysaccharide, or (a) and/or(b) can be treated to be made reactive with each other. In some aspects(a) and (b) are disposed separately on the surface to form the sealantcoating. The natural biodegradable polysaccharide can be the same typesof polymers of different types of polymers.

The first coupling group and second coupling group can be a pair ofchemical groups that are reactive with one another, preferablyspecifically reactive. The groups can also become reactive with eachother upon addition of a particular agent to the mixture of naturalbiodegradable polysaccharide having different reactive groups.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of cumulative BSA release from maltodextrin-acrylatefilaments treated with amylase, over a period of time.

FIG. 2 is a graph of cumulative BSA release frommaltodextrin-acrylate/photo-PVP-coated PEBAX rod treated with amylase,over a period of time.

FIG. 3 is a graph of cumulative absorbance values of active and totalIgG Fab fragment release from maltodextrin-acrylate filaments treatedwith amylase, over a period of time.

FIG. 4 is a graph of cumulative absorbance values of active and totalIgG release from maltodextrin-acrylate(redox)/photo-PVP-coated stainlesssteel rods treated with amylase, over a period of time.

FIG. 5 is a graph of cumulative absorbance values of active and totalIgG release from maltodextrin-acrylate(photoinitiation)/photo-PVP-coatedstainless steel rods treated with amylase and percent degradation of themaltodextrin-acrylate coating, over a period of time.

FIG. 6 is a graph of cumulative absorbance values of active and totalIgG release from a maltodextrin-acrylate filament treated with amylaseand percent degradation of the filament, over a period of time.

FIG. 7 is a graph of modulus of a maltodextrin-acrylate matrix formedvia REDOX polymerization, over a period of time.

FIG. 8 is a graph of repetitive force testing of maltodextrin-acrylatecoated PEBAX rods versus synthetic polymer-coated PEBAX rods.

DETAILED DESCRIPTION

The embodiments of the present invention described herein are notintended to be exhaustive or to limit the invention to the precise formsdisclosed in the following detailed description. Rather, the embodimentsare chosen and described so that others skilled in the art canappreciate and understand the principles and practices of the presentinvention.

All publications and patents mentioned herein are hereby incorporated byreference. The publications and patents disclosed herein are providedsolely for their disclosure. Nothing herein is to be construed as anadmission that the inventors are not entitled to antedate anypublication and/or patent, including any publication and/or patent citedherein.

In one aspect, the invention provides methods of preparing biodegradablecoatings that release bioactive agents from the surface of medicaldevices. The compositions and methods of the present invention areparticularly useful for coating surfaces of implantable medical devices,such as stents and catheters, and that are capable of releasing drugsfrom the device.

In another aspect, the invention provides methods of preparingbiodegradable articles, such as medical implants or in vivo formedmatrices. The biodegradable articles can also be used for the release ofbioactive agents, and in this manner can function as bioactiveagent-releasing implants or depots. In some aspects, the biodegradablearticles of the invention biodegrade within a period that is acceptablefor the desired application.

In some aspects, the biodegradable article is a medical implant thatprovides mechanical properties at the implantation site and maintainsthese mechanical properties until they are no longer needed. After thisperiod of time has elapsed, the medical implant is degraded to an extentthat the properties are no longer provided by the medical implant, andthe biodegradable components can be absorbed and/or excreted by thebody. In some embodiments, the medical implant slowly degrades andtransfers stress at the appropriate rate to surrounding tissues as thesetissues heal and can accommodate the stress once borne by the medicaldevice.

The biodegradable coating or article includes a natural biodegradablepolysaccharide having a coupling group. Exemplary natural biodegradablepolysaccharides include amylose and maltodextrin. In some aspects, thepresent invention provides biodegradable coatings having excellentsurface characteristics and that can provide a suitable vehicle for thedelivery of bioactive agents. These biodegradable coatings can bedisposed on medical devices having a variety of biomaterial surfaces.

In some embodiments of the invention, a coating is formed on a devicethat includes a biodegradable matrix and biodegradable microparticles,the biodegradable microparticles including one or more bioactive agents.The biodegradable material used to form the matrix includes a naturalbiodegradable polysaccharide as a component. In the matrix, naturalbiodegradable polysaccharides such as amylose and maltodextrin arecoupled to each other and the biodegradable microparticles areassociated with the matrix.

In yet other embodiments of the invention, a sealant coating is formedon a device. The sealant coating includes a biodegradable matrix andoptionally one or more bioactive agents, such as prothrombotic agents.

The sealant coating of the invention can, at least initially, provide abarrier on the porous surface that is not permeable to fluids within thebody. Gradually, the sealant coating degrades and its function isreplaced by tissue that infiltrates the porous surface. Therefore, thesealant coating has particular properties, such as biodegradability andrelative impermeability (i.e., relative to the degradation of thesealant coating). The sealant coating can also be compliant and/orconformal, and can have properties such as flexibility, elasticity, andbendability.

As used herein, impermeable, used in relation to the function of thesealant coating, refers to a significant reduction in the transmissionof bulk liquid or fluids through the substrate which the sealant coatingis associated with. For example, the sealant coating can be impermeableto the transmission of blood. The impermeability can be maintained asthe natural biodegradable polysaccharide-based sealant coating degrades,and is replaced by tissue.

As referred to herein, a “natural biodegradable polysaccharide” refersto a non-synthetic polysaccharide that is capable of being enzymaticallydegraded but that is generally non-enzymatically hydrolytically stable.Natural biodegradable polysaccharides include polysaccharide and/orpolysaccharide derivatives that are obtained from natural sources, suchas plants or animals. Natural biodegradable polysaccharides include anypolysaccharide that has been processed or modified from a naturalbiodegradable polysaccharide (for example, maltodextrin is a naturalbiodegradable polysaccharide that is processed from starch). Exemplarynatural biodegradable polysaccharides include hyaluronic acid, starch,dextran, heparin, chondroitin sulfate, dermatan sulfate, heparansulfate, keratan sulfate, dextran sulfate, pentosan polysulfate, andchitosan. Preferred polysaccharides are low molecular weight polymersthat have little or no branching, such as those that are derived fromand/or found in starch preparations, for example, amylose andmaltodextrin. Therefore, the natural biodegradable polysaccharide can bea substantially non-branched or non-branched poly(glucopyranose)polymer.

Because of the particular utility of the amylose and maltodextrinpolymers, it is preferred that natural biodegradable polysaccharideshaving an average molecular weight of 500,000 Da or less, 250,000 Da orless, 100,000 Da or less, or 50,000 Da or less. It is also preferredthat the natural biodegradable polysaccharides have an average molecularweight of 500 Da or greater. A particularly preferred size range for thenatural biodegradable polysaccharides is in the range of about 1000 Dato about 10,000 Da. Natural biodegradable polysaccharides of particularmolecular weights can be obtained commercially or can be prepared. Thedecision of using natural biodegradable polysaccharides of a particularsize range may depend on factors such as the physical characteristics ofthe coating composition (e.g., viscosity), the desired rate ofdegradation of the coating, the presence of other optional moieties inthe coating composition, for example, bioactive agents, etc.

As used herein, “amylose” or “amylose polymer” refers to a linearpolymer having repeating glucopyranose units that are joined by α-1,4linkages. Some amylose polymers can have a very small amount ofbranching via α-1,6 linkages (about less than 0.5% of the linkages) butstill demonstrate the same physical properties as linear (unbranched)amylose polymers do. Generally amylose polymers derived from plantsources have molecular weights of about 1×10⁶ Da or less. Amylopectin,comparatively, is a branched polymer having repeating glucopyranoseunits that are joined by α-1,4 linkages to form linear portions and thelinear portions are linked together via α-1,6 linkages. The branch pointlinkages are generally greater than 1% of the total linkages andtypically 4%-5% of the total linkages. Generally amylopectin derivedfrom plant sources have molecular weights of 1×10⁷ Da or greater.

Amylose can be obtained from, or is present in, a variety of sources.Typically, amylose is obtained from non-animal sources, such as plantsources. In some aspects, a purified preparation of amylose is used asstarting material for the preparation of the amylose polymer havingcoupling groups. In other aspects, as starting material, amylose can beused in a mixture that includes other polysaccharides.

For example, in some aspects, starch preparations having a high amylosecontent, purified amylose, synthetically prepared amylose, or enrichedamylose preparations can be used in the preparation of amylose havingthe coupling groups. In starch sources, amylose is typically presentalong with amylopectin, which is a branched polysaccharide. According tothe invention, it is preferred to use coating compositions that includeamylose, wherein the amylose is present in the composition in an amountgreater than amylopectin, if present in the composition. For example, insome aspects, starch preparations having high amylose content, purifiedamylose, synthetically prepared amylose, or enriched amylosepreparations can be used in the preparation of amylose polymer havingthe coupling groups. In some embodiments the composition includes amixture of polysaccharides including amylose wherein the amylose contentin the mixture of polysaccharides is 50% or greater, 60% or greater, 70%or greater, 80% or greater, or 85% or greater by weight. In otherembodiments the composition includes a mixture of polysaccharidesincluding amylose and amylopectin and wherein the amylopectin content inthe mixture of polysaccharides is 30% or less, or 15% or less. In somecases it may be desirable to use non-retrograding starches, such as waxystarch, in the current invention. The amount of amylopectin present in astarch may also be reduced by treating the starch with amylopectinase,which cleaves α-1,6 linkages resulting in the debranching of amylopectininto amylose.

In some cases a synthesis reaction can be carried out to prepare anamylose polymer having pendent coupling groups (for example, amylosewith pendent ethylenically unsaturated groups) and steps may beperformed before, during, and/or after the synthesis to enrich theamount of amylose, or purify the amylose.

Amylose of a particular size, or a combination of particular sizes canbe used. The choice of amylose in a particular size range may depend onthe application, for example, the type of surface coated or the porosityof the surface. In some embodiments amylose having an average molecularweight of 500,000 Da or less, 250,000 Da or less, 100,000 Da or less,50,000 Da or less, preferably greater than 500 Da, or preferably in therange of about 1000 Da to about 10,000 Da is used. Amylose of particularmolecular weights can be obtained commercially or can be prepared. Forexample, synthetic amyloses with average molecular masses of 70, 110,320, and 1,000 kDa can be obtained from Nakano Vinegar Co., Ltd. (Aichi,Japan). The decision of using amylose of a particular size range maydepend on factors such as the physical characteristics of the coatingcomposition (e.g., viscosity), the desired rate of degradation of thecoating, the presence of other optional moieties in the coatingcomposition (for example, bioactive agents, etc.), etc.

Maltodextrin is typically generated by hydrolyzing a starch slurry withheat-stable α-amylase at temperatures at 85-90° C. until the desireddegree of hydrolysis is reached and then inactivating the α-amylase by asecond heat treatment. The maltodextrin can be purified by filtrationand then spray dried to a final product. Maltodextrins are typicallycharacterized by their dextrose equivalent (DE) value, which is relatedto the degree of hydrolysis defined as: DE=MW dextrose/number-averagedMW starch hydrolysate×100.

A starch preparation that has been totally hydrolyzed to dextrose(glucose) has a DE of 100, where as starch has a DE of about zero. A DEof greater than 0 but less than 100 characterizes the mean-averagemolecular weight of a starch hydrolysate, and maltodextrins areconsidered to have a DE of less than 20. Maltodextrins of variousmolecular weights, for example, in the range of about 500-5000 Da arecommercially available (for example, from CarboMer, San Diego, Calif.).

Another contemplated class of natural biodegradable polysaccharides isnatural biodegradable non-reducing polysaccharides. A non-reducingpolysaccharide can provide an inert matrix thereby improving thestability of sensitive bioactive agents, such as proteins and enzymes. Anon-reducing polysaccharide refers to a polymer of non-reducingdisaccharides (two monosaccharides linked through their anomericcenters) such as trehalose (α-D-glucopyranosyl α-D-glucopyranoside) andsucrose (β-D-fructofuranosyl α-D-glucopyranoside). An exemplarynon-reducing polysaccharide comprises polyalditol which is availablefrom GPC (Muscatine, Iowa). In another aspect, the polysaccharide is aglucopyranosyl polymer, such as a polymer that includes repeating(1→3)O-β-D-glucopyranosyl units.

In some aspects, the coating compositions can include naturalbiodegradable polysaccharides that include chemical modifications otherthan the pendent coupling group. To exemplify this aspect, modifiedamylose having esterified hydroxyl groups can be prepared and used insealant coating compositions in association with the methods of theinvention. Other natural biodegradable polysaccharides having hydroxylgroups may be modified in the same manner. These types of modificationscan change or improve the properties of the natural biodegradablepolysaccharide making for a coating composition that is particularlysuitable for a desired application. Many chemically modified amylosepolymers, such as chemically modified starch, have at least beenconsidered acceptable food additives.

As used herein, “modified natural biodegradable polysaccharides” refersto chemical modifications to the natural biodegradable polysaccharidethat are different than those provided by the coupling group or theinitiator group. Modified amylose polymers having a coupling group(and/or initiator group) can be used in the compositions and methods ofthe invention.

To exemplify this aspect, modified amylose is described. By chemicallymodifying the hydroxyl groups of the amylose, the physical properties ofthe amylose can be altered. The hydroxyl groups of amylose allow forextensive hydrogen bonding between amylose polymers in solution and canresult in viscous solutions that are observed upon heating and thencooling amylose-containing compositions such as starch in solution(retrograding). The hydroxyl groups of amylose can be modified to reduceor eliminate hydrogen bonding between molecules thereby changing thephysical properties of amylose in solution.

Therefore, in some embodiments the natural biodegradablepolysaccharides, such as amylose, can include one or more modificationsto the hydroxyl groups wherein the modifications are different thanthose provided by coupling group. Modifications include esterificationwith acetic anhydride (and adipic acid), succinic anhydride,1-octenylsuccinic anhydride, phosphoryl chloride, sodiumtrimetaphosphate, sodium tripolyphosphate, and sodium monophosphate;etherification with propylene oxide, acid modification with hydrochloricacid and sulfuric acids; and bleaching or oxidation with hydrogenperoxide, peracetic acid, potassium permanganate, and sodiumhypochlorite.

Examples of modified amylose polymers include carboxymethyl amylose,carboxyethyl amylose, ethyl amylose, methyl amylose, hydroxyethylamylose, hydroxypropyl amylose, acetyl amylose, amino alkyl amylose,allyl amylose, and oxidized amylose. Other modified amylose polymersinclude succinate amylose and oxtenyl succinate amylose.

In another aspect of the invention, the natural biodegradablepolysaccharide is modified with a hydrophobic moiety in order to providea biodegradable matrix having hydrophobic properties. Exemplaryhydrophobic moieties include those previously listed, fatty acids andderivatives thereof, and C₂-C₁₈ alkyl chains. A polysaccharide, such asamylose or maltodextrin, can be modified with a compound having ahydrophobic moiety, such as a fatty acid anhydride. The hydroxyl groupof a polysaccharide can also cause the ring opening of lactones toprovide pendent open-chain hydroxy esters.

In some aspects, the hydrophilic moiety pendent from the naturalbiodegradable has properties of a bioactive agent. The hydrophilicmoiety can be hydrolyzed from the natural biodegradable polymer andreleased from the matrix to provide a therapeutic effect. One example ofa therapeutically useful hydrophilic moiety is butyric acid, which hasbeen shown to elicit tumor cell differentiation and apoptosis, and isthought to be useful for the treatment of cancer and other blooddiseases. The hydrophilic moiety that provides a therapeutic effect canalso be a natural compound (such as butyric acid). Therefore,degradation of the matrix having a coupled therapeutic agent can resultin all natural degradation products.

According to the invention, a natural biodegradable polysaccharide thatincludes a coupling group is used to form an article or a coating on thesurface of a medical article. Other polysaccharides can also be presentin the coating composition. For example, the two or more naturalbiodegradable polysaccharides are used to form an article or a coatingon the surface of a medical article. Examples include amylose and one ormore other natural biodegradable polysaccharide(s), and maltodextrin andone or more other natural biodegradable polysaccharide(s); in one aspectthe composition includes a mixture of amylose and maltodextrin,optionally with another natural biodegradable polysaccharide.

In one preferred embodiment, amylose or maltodextrin is the primarypolysaccharide. In some embodiments, the composition includes a mixtureof polysaccharides including amylose or maltodextrin and the amylose ormaltodextrin content in the mixture of polysaccharides is 50% orgreater, 60% or greater, 70% or greater, 80% or greater, or 85% orgreater by weight.

Purified or enriched amylose preparations can be obtained commerciallyor can be prepared using standard biochemical techniques such aschromatography. In some aspects, high-amylose cornstarch can be used.

As used herein, “coupling group” can include (1) a chemical group thatis able to form a reactive species that can react with the same orsimilar chemical group to form a bond that is able to couple the naturalbiodegradable polysaccharides together (for example, wherein theformation of a reactive species can be promoted by an initiator); or (2)a pair of two different chemical groups that are able to specificallyreact to form a bond that is able to couple the natural biodegradablepolysaccharides together. The coupling group can be attached to anysuitable natural biodegradable polysaccharide, including the amylose andmaltodextrin polymers as exemplified herein.

Contemplated reactive pairs include Reactive Group A and correspondingReactive Group B as shown in the Table 1 below. For the preparation of acoating composition, a reactive group from group A can be selected andcoupled to a first set of natural biodegradable polysaccharides and acorresponding reactive group B can be selected and coupled to a secondset of natural biodegradable polysaccharides. Reactive groups A and Bcan represent first and second coupling groups, respectively. At leastone and preferably two, or more than two reactive groups are coupled toan individual natural biodegradable polysaccharide polymer. The firstand second sets of natural biodegradable polysaccharides can be combinedand reacted, for example, thermochemically, if necessary, to promote thecoupling of natural biodegradable polysaccharides and the formation of anatural biodegradable polysaccharide matrix. TABLE 1 Reactive group AReactive group B amine, hydroxyl, sulfhydryl N-oxysuccinimide (“NOS”)amine Aldehyde amine Isothiocyanate amine, sulfhydryl Bromoacetyl amine,sulfhydryl Chloroacetyl amine, sulfhydryl Iodoacetyl amine, hydroxylAnhydride aldehyde Hydrazide amine, hydroxyl, carboxylic acid Isocyanateamine, sulfhydryl Maleimide sulfhydryl Vinylsulfone

Amine also includes hydrazide (R—NH—NH₂)

For example, a suitable coupling pair would be a natural biodegradablepolysaccharide having an electrophilic group and a natural biodegradablepolysaccharide having a nucleophilic group. An example of a suitableelectrophilic-nucleophilic pair is N-hydroxysuccinimide-amine pair,respectively. Another suitable pair would be an oxirane-amine pair.

In some aspects, the natural biodegradable polysaccharides of theinvention include at least one, and more typically more than one,coupling group per natural biodegradable polysaccharide, allowing for aplurality of natural biodegradable polysaccharides to be coupled inlinear and/or branched manner. In some preferred embodiments, thenatural biodegradable polysaccharide includes two or more pendentcoupling groups.

In some aspects, the coupling group on the natural biodegradablepolysaccharide is a polymerizable group. In a free radicalpolymerization reaction the polymerizable group can couple naturalbiodegradable polysaccharides together in the composition, therebyforming a biodegradable natural biodegradable polysaccharide matrix.

A preferred polymerizable group is an ethylenically unsaturated group.Suitable ethylenically unsaturated groups include vinyl groups, acrylategroups, methacrylate groups, ethacrylate groups, 2-phenyl acrylategroups, acrylamide groups, methacrylamide groups, itaconate groups, andstyrene groups. Combinations of different ethylenically unsaturatedgroups can be present on a natural biodegradable polysaccharide, such asamylose or maltodextrin.

In preparing the natural biodegradable polysaccharide having pendentcoupling groups any suitable synthesis procedure can be used. Suitablesynthetic schemes typically involve reaction of, for example, hydroxylgroups on the natural biodegradable polysaccharide, such as amylose ormaltodextrin. Synthetic procedures can be modified to produce a desirednumber of coupling groups pendent from the natural biodegradablepolysaccharide backbone. For example, the hydroxyl groups can be reactedwith a coupling group-containing compound or can be modified to bereactive with a coupling group-containing compound. The number and/ordensity of acrylate groups can be controlled using the present method,for example, by controlling the relative concentration of reactivemoiety to saccharide group content.

In some modes of practice, the biodegradable polysaccharides have anamount of pendent coupling groups of about 0.7 μmoles of coupling groupper milligram of natural biodegradable polysaccharide. In a preferredaspect, the amount of coupling group per natural biodegradablepolysaccharide is in the range of about 0.3 mmoles/mg to about 0.7mmoles/mg. For example, amylose or maltodextrin can be reacted with anacrylate groups-containing compound to provide an amylose ormaltodextrin macromer having a acrylate group load level in the range ofabout 0.3 mmoles/mg to about 0.7 μmoles/mg.

As used herein, an “initiator” refers to a compound, or more than onecompound, that is capable of promoting the formation of a reactivespecies from the coupling group. For example, the initiator can promotea free radical reaction of natural biodegradable polysaccharide having acoupling group. In one embodiment the initiator is a photoreactive group(photoinitiator) that is activated by radiation. In some embodiments,the initiator can be an “initiator polymer” that includes a polymerhaving a backbone and one or more initiator groups pendent from thebackbone of the polymer.

In some aspects the initiator is a compound that is light sensitive andthat can be activated to promote the coupling of the amylose polymer viaa free radical polymerization reaction. These types of initiators arereferred to herein as “photoinitiators.” In some aspects it is preferredto use photoinitiators that are activated by light wavelengths that haveno or a minimal effect on a bioactive agent if present in thecomposition. A photoinitiator can be present in a sealant compositionindependent of the amylose polymer or pendent from the amylose polymer.

In some embodiments, photoinitiation occurs using groups that promote anintra- or intermolecular hydrogen abstraction reaction. This initiationsystem can be used without additional energy transfer acceptor moleculesand utilizing nonspecific hydrogen abstraction, but is more commonlyused with an energy transfer acceptor, typically a tertiary amine, whichresults in the formation of both aminoalkyl radicals and ketyl radicals.Examples of molecules exhibiting hydrogen abstraction reactivity anduseful in a polymeric initiating system, include analogs ofbenzophenone, thioxanthone, and camphorquinone.

In some preferred embodiments the photoinitiator includes one or morecharged groups. The presence of charged groups can increase thesolubility of the photoinitiator (which can contain photoreactive groupssuch as aryl ketones) in an aqueous system and therefore provide for animproved coating composition. Suitable charged groups include, forexample, salts of organic acids, such as sulfonate, phosphonate,carboxylate, and the like, and onium groups, such as quaternaryammonium, sulfonium, phosphonium, protonated amine, and the like.According to this embodiment, a suitable photoinitiator can include, forexample, one or more aryl ketone photogroups selected from acetophenone,benzophenone, anthraquinone, anthrone, anthrone-like heterocycles, andderivatives thereof; and one or more charged groups, for example, asdescribed herein. Examples of these types of water-solublephotoinitiators have been described in U.S. Pat. No. 6,077,698.

In some aspects the photoinitiator is a compound that is activated bylong-wavelength ultraviolet (UV) and visible light wavelengths. Forexample, the initiator includes a photoreducible or photo-oxidizabledye. Photoreducible dyes can also be used in conjunction with a compoundsuch as a tertiary amine. The tertiary amine intercepts the inducedtriplet producing the radical anion of the dye and the radical cation ofthe tertiary amine. Examples of molecules exhibiting photosensitizationreactivity and useful as an initiator include acridine orange,camphorquinone, ethyl eosin, eosin Y, erythrosine, fluorescein,methylene green, methylene blue, phloxime, riboflavin, rose bengal,thionine, and xanthine dyes. Use of these types of photoinitiators canbe particularly advantageous when a light-sensitive bioactive agent isincluded in the sealant coating.

Therefore, in yet another aspect, the invention provides a coatingcomposition comprising (i) a natural biodegradable polysaccharidecomprising an ethylenically unsaturated group (ii) a photoinitiatorselected from the group consisting of acridine orange, camphorquinone,ethyl eosin, eosin Y, erythrosine, fluorescein, methylene green,methylene blue, phloxime, riboflavin, rose bengal, thionine, andxanthine dyes, and (iii) a bioactive agent.

Thermally reactive initiators can also be used to promote thepolymerization of natural biodegradable polymers having pendent couplinggroups. Examples of thermally reactive initiators include 4,4′azobis(4-cyanopentanoic acid),2,2-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, and analogs ofbenzoyl peroxide. Redox initiators can also be used to promote thepolymerization of the natural biodegradable polymers having pendentcoupling groups. In general, combinations of organic and inorganicoxidizers, and organic and inorganic reducing agents are used togenerate radicals for polymerization. A description of redox initiationcan be found in Principles of Polymerization 2^(nd) Edition, Odian G.,John Wiley and Sons, pgs 201-204, (1981).

In some cases, the initiator can be included in a base coating and thenatural biodegradable polysaccharide or composition that includes thenatural biodegradable polysaccharide can be disposed on the basecoating. For example, a coated layer that includes the naturalbiodegradable polysaccharide can be formed on a coated layer thatincludes a synthetic polymer. The synthetic polymer can be a hydrophilicpolymer such as poly(vinylpyrrolidone), poly(acrylamide), or copolymersthereof. In some aspects the synthetic polymer is formed usingphotoreactive groups, such as photoreactive groups that are pendent fromthe synthetic polymer, which can be used to covalently bond thesynthetic polymer to a surface of the article.

In some aspects the polymerization initiator is a polymer that includesan initiator group (herein referred to as an “initiator polymer”). Thepolymeric portion of the initiator polymer can be obtained or preparedto have particular properties or features that are desirable for usewith a coating composition, such as a sealant coating composition. Forexample, the polymeric portion of the initiator polymer can havehydrophilic or amphoteric properties, it can include pendent chargedgroups, or it can have groups that allow it to interact with aparticular surface (this can depend on the type of surface to becoated). Optionally, or additionally, the polymer can change or improvethe properties of the coating that is formed by the amylose polymerhaving coupling groups. For example, the initiator polymer can changethe elasticity, flexibility, wettability, or softness (or combinationsthereof) of the coating formed on the surface. Certain polymers, asdescribed herein, are useful as plasticizing agents for coatings thatinclude natural biodegradable polysaccharides. Initiator groups can beadded to these plasticizing polymers and used in the compositions andmethods of the invention.

For example, in some aspects an initiator can be pendent from a naturalbiodegradable polysaccharide. Therefore, the natural biodegradablepolysaccharide is able to promote activation of polymerizable groupsthat are pendent from other natural biodegradable polysaccharides andpromote the formation of a natural biodegradable polysaccharide matrix.

In other cases, the polymeric portion of the initiator polymer caninclude, for example, acrylamide and methacrylamide monomeric units, orderivatives thereof. In some embodiments, the coating compositionincludes an initiator polymer having a photoreactive group and apolymeric portion selected from the group of acrylamide andmethacrylamide polymers and copolymers.

In some aspects, the initiator includes an oxidizing agent/reducingagent pair, a “redox pair,” to drive polymerization of the biodegradablepolysaccharide. In this case, polymerization of the biodegradablepolysaccharide is carried out upon combining one or more oxidizingagents with one or more reducing agents. Other compounds can be includedin the composition to promote polymerization of the biodegradablepolysaccharides.

When combined, the oxidizing agent and reducing agent can provide aparticularly robust initiation system and can drive the formation of apolymerized matrix of polysaccharides from a composition having a lowviscosity. A polysaccharide composition with a low viscosity may be dueto a low concentration of polysaccharide in the composition, apolysaccharide having a low average molecular weight, or combinationsthereof. Matrix formation from a polysaccharide composition having a lowviscosity is particularly advantageous in many applications, especiallyfor in situ polymerization. In some aspects of the invention, a lowviscosity polysaccharide composition is passed through a small gaugedelivery conduit, such as a needle, wherein the redox pair causes thepolymerization of the polysaccharides in situ.

In some aspects of the invention, the viscosity of the composition isabove about 5 cP, or about 10 cP or greater. In other aspects of theinvention the viscosity of the composition is between about 5 cP or 10cP and about 700 cP, or between about 5 cP or 10 cP and about 250 cP.

In order to promote polymerization of the biodegradable polysaccharidesin a composition to form a matrix, the oxidizing agent is added to thereducing agent in the presence of the one or more biodegradablepolysaccharides. For example, a composition including a biodegradablepolysaccharide and a reducing agent is added to a composition includingan oxidizing agent, or a composition including a biodegradablepolysaccharide and an oxidizing agent is added to a compositioncontaining a reducing agent. One desirable method of preparing a matrixis to combine a composition including a biodegradable polysaccharide andan oxidizing agent with a composition including a biodegradablepolysaccharide and a reducing agent. For purposes of describing thismethod, the terms “first composition” and “second composition” can beused.

The viscosities of biodegradable polysaccharide in the first and secondcompositions can be the same or can be different. Generally, though, ithas been observed that good mixing and subsequent matrix formation isobtained when the compositions have the same or similar viscosities. Inthis regard, if the same biodegradable polymer is used in the first andsecond compositions, the concentration of the biodegradable polymer maybe the same or different.

The oxidizing agent can be selected from inorganic or organic oxidizingagents, including enzymes; the reducing agent can be selected frominorganic or organic reducing agents, including enzymes. Exemplaryoxidizing agents include peroxides, including hydrogen peroxide, metaloxides, and oxidases, including glucose oxidase. Exemplary reducingagents include salts and derivatives of electropositive elemental metalssuch as Li, Na, Mg, Fe, Zn, Al, and reductases. In one mode of practice,the reducing agent is present at a concentration of about 2.5 mM orgreater when the reducing agent is mixed with the oxidizing agent. Priorto mixing, the reducing agent can be present in a composition at aconcentration of, for example, 5 mM or greater.

Other reagents can be present in the composition to promotepolymerization of the biodegradable polysaccharide. Other polymerizationpromoting compounds can be included in the composition, such as metal orammonium salts of persulfate.

Optionally, the compositions and methods of the invention can includepolymerization accelerants that can improve the efficiency ofpolymerization. Examples of useful accelerants include N-vinylcompounds, particularly N-vinyl pyrrolidone and N-vinyl caprolactam.Such accelerants can be used, for instance, at a concentration ofbetween about 0.01% and about 5%, and preferably between about 0.05% andabout 0.5%, by weight, based on the volume of the coating composition.

In some aspects, an aqueous composition that includes the naturalbiodegradable polysaccharide, such as amylose or maltodextrin havingpendent coupling groups, and a bioactive agent is obtained and used inthe method of coating a surface. In another aspect, an aqueouscomposition is used to form an article. This composition can be preparedby mixing a bioactive agent, such as a water-soluble small molecule, aprotein, or a nucleic acid, with the natural biodegradablepolysaccharide.

According to the invention, the natural biodegradable polysaccharidethat includes a coupling group is used to form a coating on the surfaceof a medical device or to form an article. Other polysaccharides canalso be present in the coating composition. For example, the coating caninclude two different natural biodegradable polysaccharides, or morethan two different natural biodegradable polysaccharides. For example,in some cases the natural biodegradable polysaccharide (such as amyloseor maltodextrin) can be present in the coating or article compositionalong with another biodegradable polymer (i.e., a secondary polymer), ormore than one other biodegradable polymer. An additional polymer orpolymers can be used to alter the properties of the matrix, or serve asbulk polymers to alter the volume of the matrix. For example, otherbiodegradable polysaccharides can be used in combination with theamylose polymer. These include hyaluronic acid, dextran, starch, amylose(for example, non-derivitized), amylopectin, cellulose, xanthan,pullulan, chitosan, pectin, inulin, alginates, and heparin.

In some aspects of the invention, a composition is disposed on a surfacethat includes at least the natural biodegradable polysaccharide, such asamylose or maltodextrin having a coupling group and a bioactive agent.In some embodiments the composition includes the natural biodegradablepolysaccharide, a bioactive agent, and an initiator. In otherembodiments, a coating is formed by disposing the natural biodegradablepolysaccharide and disposing the biodegradable microparticles on asurface. In some embodiments a composition containing both the naturalbiodegradable polysaccharide and the biodegradable microparticles havingthe bioactive agent are disposed on a surface. In yet other embodimentsof the invention, a sealant composition that includes at least thenatural biodegradable polysaccharide having a coupling group is disposedon a porous surface.

The concentration of the natural biodegradable polysaccharide in thecomposition can be chosen to provide a coating or an article having adesired density of crosslinked natural biodegradable polysaccharide. Insome embodiments, the concentration of natural biodegradablepolysaccharide in the composition can depend on the type or nature ofthe bioactive agent that is included in the composition. In someembodiments the natural biodegradable polysaccharide having the couplinggroups is present in the coating composition at a concentration in therange of 5-100% (w/v), and 5-50%, and in more specific embodiments inthe range of 10-20% and in other embodiments in the range of 20-50%(w/v).

For example, in forming a medical implant, the concentration of thenatural biodegradable polysaccharide may be higher to provide a morestructurally rigid implant.

Other polymers or non-polymeric compounds can be included in thecomposition that can change or improve the properties of the coating orarticle that is formed by the natural biodegradable coating havingcoupling groups in order to change the elasticity, flexibility,wettability, or adherent properties, (or combinations thereof) of thecoating formed on the surface.

For example, in order to improve the properties of a coating, such as asealant coating when formed, it is possible to include in the mixtureone or a combination of plasticizing agents. Suitable plasticizingagents include glycerol, diethylene glycol, sorbitol, sorbitol esters,maltitol, sucrose, fructose, invert sugars, corn syrup, and mixturesthereof. The amount and type of plasticizing agents can be readilydetermined using known standards and techniques.

Compositions of this invention can be used to coat the surface of avariety of implantable devices. The coating of natural biodegradablepolysaccharide (with or without bioactive agent) can be applied to amedical device using standard techniques to cover the entire surface ofthe device, or a portion of the device surface.

The medical articles on which the biodegradable coating can be formedcan be fabricated from any suitable biomaterial or combinations ofbiomaterials. Preferred biomaterials include those formed of syntheticpolymers, including oligomers, homopolymers, and copolymers resultingfrom either addition or condensation polymerizations.

Examples of suitable addition polymers include, but are not limited to,acrylics such as those polymerized from methyl acrylate, methylmethacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylicacid, methacrylic acid, glyceryl acrylate, glyceryl methacrylate,methacrylamide, and acrylamide; vinyls such as ethylene, propylene,vinyl chloride, vinyl acetate, vinyl pyrrolidone, and vinylidenedifluoride.

Examples of condensation polymers include, but are not limited to,nylons such as polycaprolactam, polylauryl lactam, polyhexamethyleneadipamide, and polyhexamethylene dodecanediamide, and alsopolyurethanes, polycarbonates, polyamides, polysulfones, poly(ethyleneterephthalate), polylactic acid, polyglycolic acid,polydimethylsiloxanes, and polyetherketone.

Other suitable biomaterials include metals, metal alloys, and ceramics.The metals and metal alloys include, but are not limited to, titanium,Nitinol, stainless steel, tantalum, and cobalt chromium. A second classof metals includes the noble metals such as gold, silver, copper, andplatinum uridium. The ceramics include, but are not limited to, siliconnitride, silicon carbide, zirconia, and alumina, as well as glass,silica, and sapphire. Combinations of ceramics and metals are anotherclass of biomaterials.

Certain natural materials are also suitable biomaterials, includinghuman tissue such as bone, cartilage, skin and teeth; and other organicmaterials such as wood, cellulose, compressed carbon, and rubber.

The surface of such biomaterials can be pretreated (for example, with aParylene coating composition) in order to alter the surface propertiesof the biomaterial, when desired.

The biomaterials as described herein can be used to fabricate a varietyof implantable devices on which the biodegradable coating can be formed.The medical device can be any device that is introduced temporarily orpermanently into a mammal for the prophylaxis or treatment of a medicalcondition. These devices include any that are introduced subcutaneously,percutaneously or surgically to rest within an organ, tissue, or lumenof an organ, such as arteries, veins, ventricles or atria of the heart.The device can be a biostable device, a partially degradable device, ora completely degradable device (for example, stents can be fabricatedfrom biodegradable polymeric materials).

The natural biodegradable polysaccharide coating (in some embodimentsincluding biodegradable microparticles) can be formed on the surface ofvirtually any implantable device. Exemplary implantable devices includebut are not limited to drug-delivering vascular stents; other vasculardevices (e.g., grafts, catheters, valves, artificial hearts, heartassist devices); implantable defibrillators; blood oxygenator devices;surgical devices; tissue-related materials; membranes; cell culturedevices; chromatographic support materials; biosensors; shunts forhydrocephalus; wound management devices; endoscopic devices; infectioncontrol devices; orthopedic devices; dental devices, urological devices;colostomy bag attachment devices; ophthalmic devices; glaucoma drainshunts; synthetic prostheses; intraocular lenses; respiratory,peripheral cardiovascular, spinal, neurological, dental, andear/nose/throat devices (e.g., ear drainage tubes); renal devices; anddialysis articles (e.g., tubing, membranes, grafts).

Other contemplated devices include self-expanding stents (e.g., madefrom nitinol), balloon-expanded stents (e.g., prepared from stainlesssteel), degradable coronary stents, non-degradable coronary stents,peripheral coronary stents, urinary catheters (e.g., surface-coated withantimicrobial agents), penile implants, sphincter devices, urethraldevices, bladder devices, renal devices, vascular implants and grafts,intravenous catheters (e.g., treated with antithrombotic agents), smalldiameter grafts, artificial lung catheters, electrophysiology catheters,anastomosis devices, vertebral disks, bone pins, suture anchors,hemostatic barriers, clamps, surgicalstaples/sutures/screws/plates/clips, atrial septal defect closures,electro-stimulation leads for cardiac rhythm management (e.g., pacerleads), glucose sensors (long-term and short-term), blood pressure andstent graft catheters, blood oxygenator tubing, blood oxygenatormembranes, blood bags, birth control devices, breast implants, benignprostatic hyperplasia and prostate cancer implants, bonerepair/augmentation devices, breast implants, cartilage repair devices,orthopedic joint implants, orthopedic fracture repairs, tissueadhesives, tissue sealants, tissue scaffolds, cerebral spinal fluid(CSF) shunts, dental implants, dental fracture repair devices, implanteddrug infusion tubes, intravitreal drug delivery devices, nerveregeneration conduits, oncological implants, electrostimulation leads,pain management implants, spinal/orthopedic repair devices, wounddressings, embolic protection filters, abdominal aortic aneurysm grafts,heart valves (e.g., mechanical, polymeric, tissue, percutaneous, carbon,sewing cuff), valve annuloplasty devices, mitral valve repair devices,vascular intervention devices, left ventricle assist devices, neuroaneurysm treatment coils, neurological catheters, left atrial appendagefilters, central venous access catheters, hemodialysis devices, cathetercuffs, anastomotic closures, vascular access catheters, cardiac sensors,uterine bleeding patches, urological catheters/stents/implants, in vitrodiagnostics, aneurysm exclusion devices, neuropatches, Vena cavafilters, urinary dialators, endoscopic surgical tissue extractors,atherectomy catheters, clot extraction catheters, percutaneoustransluminal angioplasty (PTA) catheters, percutaneous transluminalcoronary angioplasty (PTCA) catheters, stylets (vascular andnon-vascular), coronary guidewires, drug infusion catheters, esophagealstents, circulatory support systems, angiographic catheters, transitionsheaths and dialators, coronary and peripheral guidewires, hemodialysiscatheters, neurovascular balloon catheters, tympanostomy vent tubes,cerebro-spinal fluid shunts, defibrillator leads, percutaneous closuredevices, drainage tubes, thoracic cavity suction drainage catheters,electrophysiology catheters, stroke therapy catheters, abscess drainagecatheters, biliary drainage products, dialysis catheters, central venousaccess catheters, and parental feeding catheters.

The compositions are particularly useful for forming biodegradablecoatings on the surface of devices that will come in contact withaqueous systems. The body fluids typically have enzymes that allow forthe degradation of the natural biodegradable polysaccharide-basedcoating. The aqueous system (such as bodily fluids) allows for thedegradation of the biodegradable coating and release of the bioactiveagent from the device. In some cases, depending on the bioactive agentand the matrix, the bioactive agent can diffuse out of the matrix. Forexample, it has been demonstrated that a loosely formed matrix may allowsome diffusion of bioactive agents, particularly smaller bioactiveagents. More desirably, well-formed matrices having significationpolysaccharide association via coupling groups are able to retainbioactive agents. Release of bioactive agents from these matrices ismediated by enzymatic degradation.

The coatings can also be formed on a biological article. A “biologicalarticle” refers to any sort of non-synthetic biologically-based articlesuch as a cell or a portion of a cell, a group of cells, tissue, or anorgan or a portion of a organ. The present reagents can be used inmethods for encapsulating cellular material.

In some aspects of the invention, a sealant coating is provided on aporous surface of a medical article. The medical article can be anyarticle that is introduced into a mammal for the prophylaxis ortreatment of a medical condition, wherein the medical article include asealant coating (at least initially) and has a sealant function. Themedical article having the sealant coating can provide one or morefunctions, including providing a barrier to the movement of body fluids,such as blood.

The sealant coatings can be formed on the surface of articles that havea porous structure wherein it is desired to seal the porous structure,providing a barrier to the movement of body fluids. In many cases it isdesirable to form these artificial barriers to ensure that the implantedarticle functions as it is intended to in the body. Gradually, however,it is desired to allow the body to maintain the function of the sealantcoating by replacing the sealant barrier materials with naturalmaterials from the body.

The sealant composition can be prepared and/or applied in such a manneras to fill the pores on the surface of the article with the sealantmaterial. This can be achieved by, for example, controlling factors suchas the viscosity of the coating composition and the coupling of thenatural biodegradable polysaccharides during formation of the coating.

An article having a “porous surface” refers to any article having asurface with pores on which a natural biodegradable polysaccharide-basedsealant coating can be formed. The pores are preferably of a physicaldimension that permits in-growth of tissue into the pores as the sealantcoating degrades. The porous surface can be associated with a non-poroussurface, such as a scaffold that can provide support to the poroussurface.

The medical article can include porous surfaces that can be providedwith a sealant coating and non-porous surfaces that are not coated withthe sealant coating, optionally coated with the sealant coating, orcoated with a material that is different than the sealant coating. Allor a portion of the porous surfaces can be coated with the sealantcoating. In some cases a sealant material that is different than thenatural biodegradable polysaccharide-based sealant material can be usedin conjunction with the natural biodegradable polysaccharide-basedsealant material.

For articles that have interior and exterior porous surfaces, either theinterior or the exterior portions can be coated, or portions of theinterior and/or exterior can be coated. The portion or portions of thearticle that are coated can depend on a particular desired applicationor function of the coated article. For example, in some cases it may bedesirable to have a difference in the flow of fluids, such as blood,through porous portions of the medical article. Also, tissue in-growthon selected portions of the article can also be promoted by depositingthe sealant coating at desired locations.

The porous surface of the article can also include a material that isthrombogenic and/or presents surface stasis areas (regions of minimizedor no blood flow). Depending on the application, a surface having adesired degree of porosity is obtained. The surface will have a degreeof porosity sufficient for proper in-growth of cells and tissue formingfactors. Upon tissue in-growth, the surface can provide a barrier thatis fluid impermeable.

In many cases the porous surface of the article is a fabric or hasfabric-like qualities. The porous surface can be formed from textiles,which include woven materials, knitted materials, and braided materials.Particularly useful textile materials are woven materials which can beformed using any suitable weave pattern known in the art.

The porous surface can be that of a graft, sheath, cover, patch, sleeve,wrap, casing, and the like. These types of articles can function as themedical article itself or be used in conjunction with another part of amedical article (examples of which are described herein).

The porous surface can include any suitable type of biomaterial. Usefulbiomaterials can be woven into fibers for the preparation of fabrics asdescribed herein. Useful materials include synthetic addition orcondensation polymers such as polyesters, polypropylenes, polyethylenes,polyurethanes, and polytetrafluoroethylenes. Polyethylene terephthalate(PET) is a commonly used polymer in fabrics. Blends of these polymerscan also be utilized in the preparation of fibers, such as monofilamentor multi-filament fibers, for the construction of fabrics. Commonly usedfabrics include those such as nylon, velour, and DACRON™.

The fabrics can optionally include stiffening materials to improve thephysical properties of the article, for example, to improve the strengthof a graft. Such materials can improve the function of an implantedarticle. For example, strengthening materials can improve the patency ofthe graft.

Porous surfaces can also be formed by dipping mandrels in these types ofpolymers.

Other particular contemplated porous surfaces include those of cardiacpatches. These can be used to decrease suture line bleeding associatedwith cardiovascular reconstructions. The patches can be used to sealaround the penetrating suture. Common materials used in cardiac patchesinclude PTFE and DACRON™.

The thickness of the material used as the porous surface can be chosendepending on the application. However, it is common that thesethicknesses are about 1.0 mm or less on average, and typically in therange of about 0.10 mm to about 1.0 mm.

Other particular contemplated porous surfaces include grafts,particularly grafts having textured exterior portions. Examples oftextured grafts include those that have velour-textured exteriors, withtextured or smooth interiors. Grafts constructed from woven textileproducts are well known in the art and have been described in numerousdocuments, for example, U.S. Pat. No. 4,047,252; U.S. Pat. No.5,178,630; U.S. Pat. No. 5,282,848; and U.S. Pat. No. 5,800,514.

The natural biodegradable polysaccharide can be used to provide asealant coating to a wide variety of articles. As used herein, “article”is used in its broadest sense and includes objects such as devices. Sucharticles include, but are not limited to vascular implants and grafts,grafts, surgical devices; synthetic prostheses; vascular prosthesisincluding endoprosthesis, stent-graft, and endovascular-stentcombinations; small diameter grafts, abdominal aortic aneurysm grafts;wound dressings and wound management device; hemostatic barriers; meshand hernia plugs; patches, including uterine bleeding patches, atrialseptic defect (ASD) patches, patent foramen ovale (PFO) patches,ventricular septal defect (VSD) patches, and other generic cardiacpatches; ASD, PFO, and VSD closures; percutaneous closure devices,mitral valve repair devices; left atrial appendage filters; valveannuloplasty devices, catheters; central venous access catheters,vascular access catheters, abscess drainage catheters, drug infusioncatheters, parental feeding catheters, intravenous catheters (e.g.,treated with antithrombotic agents), stroke therapy catheters, bloodpressure and stent graft catheters; anastomosis devices and anastomoticclosures; aneurysm exclusion devices; biosensors including glucosesensors; birth control devices; breast implants; cardiac sensors;infection control devices; membranes; tissue scaffolds; tissue-relatedmaterials; shunts including cerebral spinal fluid (CSF) shunts, glaucomadrain shunts; dental devices and dental implants; ear devices such asear drainage tubes, tympanostomy vent tubes; ophthalmic devices; cuffsand cuff portions of devices including drainage tube cuffs, implanteddrug infusion tube cuffs, catheter cuff, sewing cuff; spinal andneurological devices; nerve regeneration conduits; neurologicalcatheters; neuropatches; orthopedic devices such as orthopedic jointimplants, bone repair/augmentation devices, cartilage repair devices;urological devices and urethral devices such as urological implants,bladder devices, renal devices and hemodialysis devices, colostomy bagattachment devices; biliary drainage products.

In some aspects, the polymeric compositions can be utilized inconnection with an ophthalmic article. The ophthalmic article can beconfigured for placement at an external or internal site of the eye.Suitable ophthalmic articles in accordance with these aspects canprovide bioactive agent to any desired area of the eye. In some aspects,the articles can be utilized to deliver bioactive agent to an anteriorsegment of the eye (in front of the lens), and/or a posterior segment ofthe eye (behind the lens). Suitable ophthalmic devices can also beutilized to provide bioactive agent to tissues in proximity to the eye,when desired. The biodegradable polysaccharide compositions can be usedeither for the formation of a coating on the surface of an ophthalmicarticle, or in the construction of an ophthalmic article.

Suitable external articles can be configured for topical administrationof bioactive agent. Such external devices can reside on an externalsurface of the eye, such as the cornea (for example, contact lenses) orbulbar conjunctiva. In some embodiments, suitable external devices canreside in proximity to an external surface of the eye.

Articles configured for placement at an internal site of the eye canreside within any desired area of the eye. In some aspects, theophthalmic article can be configured for placement at an intraocularsite, such as the vitreous. Illustrative intraocular devices include,but are not limited to, those described in U.S. Pat. No. 6,719,750 B2(“Devices for Intraocular Drug Delivery,” Vamer et al.) and U.S. Pat.No. 5,466,233 (“Tack for Intraocular Drug Delivery and Method forInserting and Removing Same,” Weiner et al.); U.S. Publication Nos.2005/0019371 A1 (“Controlled Release Bioactive Agent Delivery Device,”Anderson et al.), 2004/0133155 A1 (“Devices for Intraocular DrugDelivery,” Vamer et al.), 2005/0059956 A1 (“Devices for Intraocular DrugDelivery,” Vamer et al.), and U.S. application Ser. No. 11/204,195(filed Aug. 15, 2005, Anderson et al.), Ser. No. 11/204,271 (filed Aug.15, 2005, Anderson et al.), Ser. No. 11/203,981 (filed Aug. 15, 2005,Anderson et al.), Ser. No. 11/203,879 (filed Aug. 15, 2005, Anderson etal.), Ser. No. 11/203,931 (filed Aug. 15, 2005, Anderson et al.); andrelated applications.

In some aspects of the invention, the biodegradable polysaccharidecoating is included on a non-linear intraocular device. In some aspectsof the invention, the biodegradable polysaccharide coating includes abioactive agent, such as a high molecular weight bioactive agent usefulfor treating an ocular condition.

In some aspects, the ophthalmic article can be configured for placement,or can be formed, at a subretinal area within the eye. Illustrativeophthalmic devices for subretinal application include, but are notlimited to, those described in U.S. Patent Publication No. 2005/0143363(“Method for Subretinal Administration of Therapeutics IncludingSteroids; Method for Localizing Pharmacodynamic Action at the Choroidand the Retina; and Related Methods for Treatment and/or Prevention ofRetinal Diseases,” de Juan et al.); U.S. application Ser. No. 11/175,850(“Methods and Devices for the Treatment of Ocular Conditions,” de Juanet al.); and related applications.

In some aspects, the invention provides a biodegradable implant that isformed from the biodegradable polysaccharide and that includes abioactive agent, such as a high molecular weight bioactive agent usefulfor treating an ocular condition.

In some aspects, the invention provides a method for forming an articlefrom the biodegradable polysaccharide, wherein the method includespolymerizing a composition that includes the biodegradablepolysaccharide within the eye, such as in a subretinal area or withinthe vitreous. For example, a low viscosity composition including anatural biodegradable polysaccharide and a redox pair to promotepolymerization for in situ matrix formation.

Ophthalmic articles can also be configured for placement within anydesired tissues of the eye. For example, ophthalmic devices can beconfigured for placement at a subconjunctival area of the eye, such asdevices positioned extrasclerally but under the conjunctiva, such asglaucoma drainage devices and the like.

A medical article having a biodegradable coating can also be prepared byassembling an article having two or more “parts” (for example, pieces ofa medical article that can be put together to form the article) whereinat least one of the parts has a biodegradable coating. All or a portionof the part of the medical article can have a biodegradable coating. Inthis regard, the invention also contemplates parts of medical article(for example, not the fully assembled article) that have a naturalbiodegradable polysaccharide-based coating.

In some aspects of the invention the natural biodegradable polymer isused to form the body member of a medical implant, wherein the bodymember has a wet weight of about 10 g or less, or a dry weight of about2.5 g or less.

The device can also have a base coating of material. The base coatingcan serve one or more functions, for example, it can provide an improvedsurface for the natural biodegradable polysaccharide or composition thatincludes the natural biodegradable polysaccharide. The base coating caninclude a polymeric material, such as a natural or synthetic polymer.Examples of suitable compounds that can be used to pretreat a surface toprovide a base coat include Parylene and organosilane compounds.Suitable base coatings can include, for example, methacrylate, acrylate,alkylacrylate, acrylamide, vinylpyrrolidinone, vinylacetamide, and vinylformamide based polymers and copolymers. These polymers can also includelatent reactive groups such as photoreactive groups.

Base coatings can be useful in various coating processes. For example,in some aspects, biodegradable microparticles can be first disposed on abase coat and then the natural biodegradable polysaccharide havingcoupling groups can be disposed on the microparticles. The surface canthen be treated to form a coating wherein the microparticles arepredominantly located between the base layer and the layer formed fromthe natural biodegradable polysaccharide having coupling groups. Ifdesired, an initiator can be included in a base coating and the naturalbiodegradable polysaccharide polymer or composition that includes thenatural biodegradable polysaccharide polymer can be disposed on the basecoating. The base coating can serve one or more functions, for example,it can provide an improved surface for the natural biodegradablepolysaccharide or composition that includes the natural biodegradablepolysaccharide.

In many aspects of the invention, the natural biodegradablepolysaccharide coating or the biodegradable article includes one or morebioactive agents. The bioactive agent can be dispersed within thenatural biodegradable polysaccharide coating or biodegradable articleitself. Alternatively, the bioactive agent can be present inmicroparticles that are associated with the natural biodegradablepolysaccharide coating. The bioactive agent can be delivered from thecoated surface upon degradation of the natural biodegradablepolysaccharide and/or biodegradable microparticles.

The term “bioactive agent” refers to a peptide, protein, carbohydrate,nucleic acid, lipid, polysaccharide, synthetic inorganic or organicmolecule, viral particle, cell, or combinations thereof, that causes abiological effect when administered in vivo to an animal, including butnot limited to birds and mammals, including humans. Nonlimiting examplesare antigens, enzymes, hormones, receptors, peptides, and gene therapyagents. Examples of suitable gene therapy agents include (a) therapeuticnucleic acids, including antisense DNA, antisense RNA, and interferenceRNA, and (b) nucleic acids encoding therapeutic gene products, includingplasmid DNA and viral fragments, along with associated promoters andexcipients. Examples of other molecules that can be incorporated includenucleosides, nucleotides, vitamins, minerals, and steroids.

Although not limited to such, the coatings of the invention areparticularly useful for delivering bioactive agents that are largehydrophilic molecules, such as polypeptides (including proteins andpeptides), nucleic acids (including DNA and RNA), polysaccharides(including heparin), as well as particles, such as viral particles, andcells. In one aspect, the bioactive agent has a molecular weight ofabout 10,000 or greater.

Classes of bioactive agents which can be incorporated into biodegradablecoatings (both the natural biodegradable matrix and/or the biodegradablemicroparticles) of this invention include, but are not limited to: ACEinhibitors, actin inhibitors, analgesics, anesthetics,anti-hypertensives, anti polymerases, antisecretory agents, anti-AIDSsubstances, antibiotics, anti-cancer substances, anti-cholinergics,anti-coagulants, anti-convulsants, anti-depressants, anti-emetics,antifungals, anti-glaucoma solutes, antihistamines, antihypertensiveagents, anti-inflammatory agents (such as NSAIDs), anti metabolites,antimitotics, antioxidizing agents, anti-parasite and/or anti-Parkinsonsubstances, antiproliferatives (including antiangiogenesis agents),anti-protozoal solutes, anti-psychotic substances, anti-pyretics,antiseptics, anti-spasmodics, antiviral agents, calcium channelblockers, cell response modifiers, chelators, chemotherapeutic agents,dopamine agonists, extracellular matrix components, fibrinolytic agents,free radical scavengers, growth hormone antagonists, hypnotics,immunosuppressive agents, immunotoxins, inhibitors of surfaceglycoprotein receptors, microtubule inhibitors, miotics, musclecontractants, muscle relaxants, neurotoxins, neurotransmitters, opioids,photodynamic therapy agents, prostaglandins, remodeling inhibitors,statins, steroids, thrombolytic agents, tranquilizers, vasodilators, andvasospasm inhibitors.

Antibiotics are art recognized and are substances which inhibit thegrowth of or kill microorganisms. Examples of antibiotics includepenicillin, tetracycline, chloramphenicol, minocycline, doxycycline,vancomycin, bacitracin, kanamycin, neomycin, gentamycin, erythromycin,cephalosporins, geldanamycin, and analogs thereof. Examples ofcephalosporins include cephalothin, cephapirin, cefazolin, cephalexin,cephradine, cefadroxil, cefamandole, cefoxitin, cefaclor, cefuroxime,cefonicid, ceforanide, cefotaxime, moxalactam, ceftizoxime, ceftriaxone,and cefoperazone.

Antiseptics are recognized as substances that prevent or arrest thegrowth or action of microorganisms, generally in a nonspecific fashion,e.g., by inhibiting their activity or destroying them. Examples ofantiseptics include silver sulfadiazine, chlorhexidine, glutaraldehyde,peracetic acid, sodium hypochlorite, phenols, phenolic compounds,iodophor compounds, quaternary ammonium compounds, and chlorinecompounds.

Anti-viral agents are substances capable of destroying or suppressingthe replication of viruses. Examples of anti-viral agents includeα-methyl-P-adamantane methylamine, hydroxy-ethoxymethylguanine,adamantanamine, 5-iodo-2′-deoxyuridine, trifluorothymidine, interferon,and adenine arabinoside.

Enzyme inhibitors are substances that inhibit an enzymatic reaction.Examples of enzyme inhibitors include edrophonium chloride,N-methylphysostigmine, neostigmine bromide, physostigmine sulfate,tacrine HCl, tacrine, 1-hydroxymaleate, iodotubercidin,p-bromotetramisole, 10-(α-diethylaminopropionyl)-phenothiazinehydrochloride, calmidazolium chloride,hemicholinium-3,3,5-dinitrocatechol, diacylglycerol kinase inhibitor I,diacylglycerol kinase inhibitor II, 3-phenylpropargylamine,N-monomethyl-L-arginine acetate, carbidopa, 3-hydroxybenzylhydrazineHCl, hydralazine HCl, clorgyline HCl, deprenyl HCl, L(−), deprenyl HCl,D(+), hydroxylamine HCl, iproniazid phosphate,6-MeO-tetrahydro-9H-pyrido-indole, nialamide, pargyline HCl, quinacrineHCl, semicarbazide HCl, tranylcypromine HCl,N,N-diethylaminoethyl-2,2-diphenylvalerate hydrochloride,3-isobutyl-1-methylxanthine, papaverine HCl, indomethacin,2-cyclooctyl-2-hydroxyethylamine hydrochloride,2,3-dichloro-α-methylbenzylamine (DCMB),8,9-dichloro-2,3,4,5-tetrahydro-1H-2-benzazepine hydrochloride,p-aminoglutethimide, p-aminoglutethimide tartrate, R(+),p-aminoglutethimide tartrate, S(−), 3-iodotyrosine,alpha-methyltyrosine, L(−) alpha-methyltyrosine, D L(−), cetazolamide,dichlorphenamide, 6-hydroxy-2-benzothiazolesulfonamide, and allopurinol.

Anti-pyretics are substances capable of relieving or reducing fever.Anti-inflammatory agents are substances capable of counteracting orsuppressing inflammation. Examples of such agents include aspirin(salicylic acid), indomethacin, sodium indomethacin trihydrate,salicylamide, naproxen, colchicine, fenoprofen, sulindac, diflunisal,diclofenac, indoprofen and sodium salicylamide. Local anesthetics aresubstances that have an anesthetic effect in a localized region.Examples of such anesthetics include procaine, lidocaine, tetracaine anddibucaine.

Cell response modifiers are chemotactic factors such as platelet-derivedgrowth factor (pDGF). Other chemotactic factors includeneutrophil-activating protein, monocyte chemoattractant protein,macrophage-inflammatory protein, SIS (small inducible secreted)proteins, platelet factor, platelet basic protein, melanoma growthstimulating activity, epidermal growth factor, transforming growthfactor (alpha), fibroblast growth factor, platelet-derived endothelialcell growth factor, insulin-like growth factor, nerve growth factor, andbone growth/cartilage-inducing factor (alpha and beta). Other cellresponse modifiers are the interleukins, interleukin inhibitors orinterleukin receptors, including interleukin 1 through interleukin 10;interferons, including alpha, beta and gamma; hematopoietic factors,including erythropoietin, granulocyte colony stimulating factor,macrophage colony stimulating factor and granulocyte-macrophage colonystimulating factor; tumor necrosis factors, including alpha and beta;transforming growth factors (beta), including beta-1, beta-2, beta-3,inhibin, activin, and DNA that encodes for the production of any ofthese proteins.

Examples of statins include lovastatin, pravastatin, simvastatin,fluvastatin, atorvastatin, cerivastatin, rousvastatin, and superstatin.

Imaging agents are agents capable of imaging a desired site, e.g.,tumor, in vivo, can also be included in the coating composition.Examples of imaging agents include substances having a label which isdetectable in vivo, e.g., antibodies attached to fluorescent labels. Theterm antibody includes whole antibodies or fragments thereof.

Exemplary ligands or receptors include antibodies, antigens, avidin,streptavidin, biotin, heparin, type IV collagen, protein A, and proteinG.

Exemplary antibiotics include antibiotic peptides.

In some aspects the bioactive agent can be selected to improve thecompatibility (for example, with blood and/or surrounding tissues) ofmedical device surfaces. These agents, referred to herein as“biocompatible agents,” when associated with the medical device surface,can serve to shield the blood from the underlying medical devicematerial. Suitable biocompatible agents preferably reduce the likelihoodfor blood components to adhere to the medical device, thus reducing theformation of thrombus or emboli (blood clots that release and traveldownstream).

The bioactive agent can improve the biocompatibility of the medicalarticle having a coating that includes the natural biodegradable polymerand the biodegradable microparticle. The bioactive agent can provideantirestenotic effects, such as antiproliferative, anti-platelet, and/orantithrombotic effects. In some embodiments, the bioactive agent caninclude anti-inflammatory agents, immunosuppressive agents, cellattachment factors, receptors, ligands, growth factors, antibiotics,enzymes, nucleic acids, and the like. Compounds having antiproliferativeeffects include, for example, actinomycin D, angiopeptin, c-mycantisense, paclitaxel, taxane, and the like.

Representative examples of bioactive agents having antithromboticeffects include heparin, heparin derivatives, sodium heparin, lowmolecular weight heparin, hirudin, lysine, prostaglandins, argatroban,forskolin, vapiprost, prostacyclin and prostacyclin analogs,D-ph-pr-arg-chloromethylketone (synthetic antithrombin), dipyridamole,glycoprotein IIb/IIIa platelet membrane receptor antibody, coproteinIIb/IIa platelet membrane receptor antibody, recombinant hirudin,thrombin inhibitor (such as commercially available from Biogen),chondroitin sulfate, modified dextran, albumin, streptokinase, tissueplasminogen activator (TPA), urokinase, nitric oxide inhibitors, and thelike.

The bioactive agent can also be an inhibitor of the GPIIb-IIIa plateletreceptor complex, which mediates platelet aggregation. GPIIb/IIIainhibitors can include monoclonal antibody Fab fragment c7E3, also knowas abciximab (ReoPro™), and synthetic peptides or peptidomimetics suchas eptifibatide (Integrilin™) or tirofiban (Agrastat™).

The bioactive agent can be an immunosuppressive agent, for example,cyclosporine, CD-34 antibody, everolimus, mycophenolic acid, sirolimus,tacrolimus, and the like.

Other exemplary therapeutic antibodies include trastuzumab (Herceptin™),a humanized anti-HER2 monoclonal antibody (moAb); alemtuzumab(Campath™), a humanized anti-CD52 moAb; gemtuzumab (Mylotarg™), ahumanized anti-CD33 moAb; rituximab (Rituxan™), a chimeric anti-CD20moAb; ibritumomab (Zevalin™), a murine moAb conjugated to abeta-emitting radioisotope; tositumomab (Bexxar™), a murine anti-CD20moAb; edrecolomab (Panorex™), a murine anti-epithelial cell adhesionmolecule moAb; cetuximab (Erbitux™), a chimeric anti-EGFR moAb; andbevacizumab (Avastin™), a humanized anti-VEGF moAb.

Additionally, the bioactive agent can be a surface adhesion molecule orcell-cell adhesion molecule. Exemplary cell adhesion molecules orattachment proteins (such as extracellular matrix proteins includingfibronectin, laminin, collagen, elastin, vitronectin, tenascin,fibrinogen, thrombospondin, osteopontin, von Willibrand Factor, bonesialoprotein (and active domains thereof), or a hydrophilic polymer suchas hyaluronic acid, chitosan or methyl cellulose, and other proteins,carbohydrates, and fatty acids. Exemplary cell-cell adhesion moleculesinclude N-cadherin and P-cadherin and active domains thereof.

Exemplary growth factors include fibroblastic growth factors, epidermalgrowth factor, platelet-derived growth factors, transforming growthfactors, vascular endothelial growth factor, bone morphogenic proteinsand other bone growth factors, and neural growth factors.

The bioactive agent can be also be selected from mono-2-(carboxymethyl)hexadecanamidopoly (ethylene glycol)₂₀₀ mono-4-benzoylbenzyl ether,mono-3-carboxyheptadecanamidopoly (ethylene glycol)₂₀₀mono-4-benzoylbenzyl ether, mono-2-(carboxymethyl) hexadecanamidotetra(ethylene glycol) mono-4-benzoylbenzyl ether,mono-3-carboxyheptadecanamidotetra (ethylene glycol)mono-4-benzoylbenzyl ether, N-[2-(4-benzoylbenzyloxy)ethyl]-2-(carboxymethyl) hexadecanamide,N-[2-(4-benzoylbenzyloxy)ethyl]-3-carboxyheptadecanamide,N-[12-(benzoylbenzyloxy) dodecyl]-2-(carboxymethyl) hexadecanamide,N-[12-(benzoylbenzyloxy)dodecyl]-3-carboxy-heptadecanamide,N-[3-(4-benzoylbenzamido)propyl]-2-(carboxymethyl) hexadecanamide,N-[3-(4-benzoylbenzamido)propyl]-3-carboxyheptadecanamide,N-(3-benzoylphenyl)-2-(carboxymethyl) hexadecanamide,N-(3-benzoylphenyl)-3-carboxyheptadecanamide,N-(4-benzoylphenyl)-2-(carboxymethyl) hexadecanamide, poly(ethyleneglycol)₂₀₀ mono-15-carboxypentadecyl mono-4-benzoylbenzyl ether, andmono-15-carboxypentadecanamidopoly (ethylene glycol)₂₀₀mono-4-benzoylbenzyl ether.

Additional examples of contemplated bioactive agents and/or bioactiveagent include analogues of rapamycin (“rapalogs”), ABT-578 from Abbott,dexamethasone, betamethasone, vinblastine, vincristine, vinorelbine,poside, teniposide, daunorubicin, doxorubicin, idarubicin,anthracyclines, mitoxantrone, bleomycins, plicamycin (mithramycin),mitomycin, mechlorethamine, cyclophosphamide and its analogs, melphalan,chlorambucil, ethylenimines and methylmelamines, alkylsulfonates-busulfan, nitrosoureas, carmustine (BCNU) and analogs,streptozocin, trazenes-dacarbazinine, methotrexate, fluorouracil,floxuridine, cytarabine, mercaptopurine, thioguanine, pentostatin,2-chlorodeoxyadenosine, cisplatin, carboplatin, procarbazine,hydroxyurea, mitotane, estrogen, ticlopidine, clopidogrel, abciximab,breveldin, cortisol, cortisone, fludrocortisone, prednisone,prednisolone, 6U-methylprednisolone, triamcinolone, acetaminophen,etodalac, tolmetin, ketorolac, ibuprofen and derivatives, mefenamicacid, meclofenamic acid, piroxicam, tenoxicam, phenylbutazone,oxyphenthatrazone, nabumetone, auranofin, aurothioglucose, gold sodiumthiomalate, azathioprine, mycophenolate mofetil; angiotensin receptorblockers; nitric oxide donors; and mTOR inhibitors.

Viral particles and viruses include those that may be therapeuticallyuseful, such as those used for gene therapy, and also attenuated viralparticles and viruses which can promote an immune response andgeneration of immunity. Useful viral particles include both natural andsynthetic types. Viral particles include, but are not limited to,adenoviruses, baculoviruses, parvoviruses, herpesviruses, poxviruses,adeno-associated viruses, vaccinia viruses, and retroviruses.

Other bioactive agents that can be used for altering gene functioninclude plasmids, phages, cosmids, episomes, and integratable DNAfragments, antisense oligonucleotides, antisense DNA and RNA, modifiedDNA and RNA, iRNA, ribozymes, siRNA, and shRNA.

Other bioactive agents include cells such as platelets, stem cells, Tlymphocytes, B lymphocytes, acidophils, adipocytes, astrocytes,basophils, hepatocytes, neurons, cardiac muscle cells, chondrocytes,epithelial cells, dendrites, endrocrine cells, endothelial cells,eosinophils, erythrocytes, fibroblasts, follicular cells, ganglioncells, hepatocytes, endothelial cells, Leydig cells, parenchymal cells,lymphocytes, lysozyme-secreting cells, macrophages, mast cells,megakaryocytes, melanocytes, monocytes, myoid cells, neck nerve cells,neutrophils, oligodendrocytes, oocytes, osteoblasts, osteochondroclasts,osteoclasts, osteocytes, plasma cells, spermatocytes, reticulocytes,Schwann cells, Sertoli cells, skeletal muscle cells, and smooth musclecells. Bioactive agents can also include genetically modified,recombinant, hybrid, mutated cells, and cells with other alterations.

Additives such as inorganic salts, BSA (bovine serum albumin), and inertorganic compounds can be used to alter the profile of bioactive agentrelease, as known to those skilled in the art.

The concentration of the bioactive agent or agents dissolved orsuspended in the coating mixture can range from about 0.01 to about 90percent, by weight, based on the weight of the final coated composition.

The particular bioactive agent, or combination of bioactive agents, canbe selected depending upon one or more of the following factors: theapplication of the controlled delivery device, the medical condition tobe treated, the anticipated duration of treatment, characteristics ofthe implantation site, the number and type of bioactive agents to beutilized, and the like.

Any of the polymer compositions described herein can be provided to thesurface of the medical article and can include any number of desiredbioactive agents, depending upon the final application of the medicaldevice.

A comprehensive listing of bioactive agents can be found in The MerckIndex, Thirteenth Edition, Merck & Co. (2001). Bioactive agents arecommercially available from Sigma Aldrich Fine Chemicals, Milwaukee,Wis.

In some aspects of the invention, the bioactive agent can be used topromote thrombosis in association with the natural biodegradablepolysaccharide-based coating, which can be of particular use when acoating having a sealant function is desired. A sealant coatingincluding a thrombogenic agent can promote the in-growth of tissue upondegradation of the sealant coating material. The degree of thrombosiscan be controlled by various factors, including, for example, thepresence of one or more thrombosis-promoting bioactive agents on orwithin the coating. Suitable thrombotic agents are described herein.

In some aspects the thrombotic agent can be selected to have an affecton the blood and/or surrounding tissues that are in contact with thearticle surface. In some cases the thrombotic agent is chosen for theability to affect the ability of blood components to adhere to themedical article. The thrombotic agent can, in some cases, be chosen topromote thrombus formation at the surface of the coated article.Therefore, in some embodiments, the sealant coating can include athrombotic agent, such as thrombin, collagen (for example, (synthetic)recombinant human collagen (FibroGen, South San Francisco, Calif.)),ADP, or convulxin to promote thrombosis at the coated surface of thearticle.

Other prothrombotic or procoagulant factors include platelet factors1-4, platelet activating factor (acetyl glyceryl ether phosphorylcholine); P-selectin and von Willebrand Factor (vWF); tissue factor;plasminogen activator initiator-1; thromboxane; procoagulantthrombin-like enzymes including cerastotin and afaâcytin; phospholipaseA₂; Ca²⁺-dependent lectins (C-type lectin); factors that bindglycoprotein receptors and induce aggregation including aggretin,rhodocytin, aggregoserpentin, triwaglerin, and equinatoxin; glycoproteinIb agonists including mamushigin and alboaggregin; vWF interactingfactors including botrocetin, bitiscetin, cerastotin, and ecarin.

Other factors, including protein factors, that are involved in theclotting cascade include coagulation factors I-XIII (for example,fibrinogen, prothrombin, tissue thromboplastin, calcium, proaccelerin(accelerator globulin), proconvertin (serum prothrombin conversionaccelerator), antihemophilic factor, plasma thromboplastin component,Stuart factor (autoprothrombin C), plasma thromboplastin antecedent(PTA), Hageman factor, and fibrin-stabilizing factor (FSF, fibrinase,protransglutaminase)).

Some surface adhesion molecule or cell-cell adhesion molecules may alsofunction to promote coagulation or thrombosis. Exemplary cell adhesionmolecules or attachment proteins (such as extracellular matrix proteins)include fibronectin, laminin, collagen, elastin, vitronectin, tenascin,fibrinogen, thrombospondin, osteopontin, von Willebrand Factor, bonesialoprotein (and active domains thereof), or a hydrophilic polymer suchas hyaluronic acid, chitosan or methyl cellulose, and other proteins,carbohydrates, and fatty acids. Exemplary cell-cell adhesion moleculesinclude N-cadherin and P-cadherin and active domains thereof.

The particular thrombotic agent, or a combination of thrombotic agentswith other bioactive agents, can be selected depending upon one or moreof the following factors: the application of the medical article, themedical condition to be treated, the anticipated duration of treatment,characteristics of the implantation site, the number and type ofthrombogenic/bioactive agents to be utilized, the chemical compositionof the sealant coating (such as amylose, selected additives, and thelike), the extent of coupling in the formed sealant coating, and thelike.

Any of the sealant compositions described herein can be provided to thesurface of the medical article. In some embodiments the sealant coatingcan include any number of desired thrombogenic/bioactive agents,depending upon the final application of the medical article. The coatingof sealant material (with or without thrombogenic/bioactive agents) canbe applied to the medical article using standard techniques to cover theentire surface of the article, or a portion of the article surface.Further, the sealant composition material can be provided as a singlecoated layer (with or without thrombogenic/bioactive agents), or asmultiple coated layers (with or without thrombogenic/bioactive agents).When multiple coated layers are provided on the surface, the materialsof each coated layer can be chosen to provide a desired effect.

In some aspects of the invention, a microparticle is used to deliver thebioactive agent from the natural biodegradable polysaccharide-basedcoating. The microparticles of the invention can comprise anythree-dimensional structure that can be immobilized on a substrate inassociation with the matrix formed by the amylose polymer. The term“microparticle” is intended to reflect that the three-dimensionalstructure is very small but not limited to a particular size range, ornot limited to a structure that has a particular shape. According to theinvention, microparticles typically have a size in the range of 5 nm to100 μm in diameter. Generally microparticles are spherical or somewhatspherical in shape, but can have other shapes as well. In preferredembodiments of the invention, the biodegradable microparticles have asize in the range of 100 nm to 20 μm in diameter, and even morepreferable in the range of 400 nm to 20 μm in diameter.

The microparticle being “biodegradable” refers to the presence of one ormore biodegradable materials in the microparticle. The biodegradablemicroparticles include at least a biodegradable material (such as abiodegradable polymer) and a bioactive agent. The biodegradablemicroparticles can gradually decompose and release bioactive agent uponexposure to an aqueous environment, such as body fluids.

The biodegradable microparticle can also include one or morebiodegradable polymers. Examples of biodegradable polymers that can beincluded in the biodegradable microparticle include, for example,polylactic acid, poly(lactide-co-glycolide), polycaprolactone,polyphosphazine, polymethylidenemalonate, polyorthoesters,polyhydroxybutyrate, polyalkeneanhydrides, polypeptides, polyanhydrides,and polyesters, and the like.

Biodegradable polyetherester copolymers can be used. Generally speaking,the polyetherester copolymers are amphiphilic block copolymers thatinclude hydrophilic (for example, a polyalkylene glycol, such aspolyethylene glycol) and hydrophobic blocks (for example, polyethyleneterephthalate). Examples of block copolymers include poly(ethyleneglycol)-based and poly(butylene terephthalate)-based blocks (PEG/PBTpolymer). Examples of these types of multiblock copolymers are describedin, for example, U.S. Pat. No. 5,980,948. PEG/PBT polymers arecommercially available from Octoplus BV, under the trade designationPolyActive™.

Biodegradable copolymers having a biodegradable, segmented moleculararchitecture that includes at least two different ester linkages canalso be used. The biodegradable polymers can be block copolymers (of theAB or ABA type) or segmented (also known as multiblock or random-block)copolymers of the (AB)_(n) type. These copolymers are formed in a two(or more) stage ring opening copolymerization using two (or more) cyclicester monomers that form linkages in the copolymer with greatlydifferent susceptibilities to transesterification. Examples of thesepolymers are described in, for example, in U.S. Pat. No. 5,252,701(Jarrett et al., “Segmented Absorbable Copolymer”).

Other suitable biodegradable polymer materials include biodegradableterephthalate copolymers that include a phosphorus-containing linkage.Polymers having phosphoester linkages, called poly(phosphates),poly(phosphonates) and poly(phosphites), are known. See, for example,Penczek et al., Handbook of Polymer Synthesis, Chapter 17:“Phosphorus-Containing Polymers,” 1077-1132 (Hans R. Kricheldorf ed.,1992), as well as U.S. Pat. Nos. 6,153,212, 6,485,737, 6,322,797,6,600,010, 6,419,709. Biodegradable terephthalate polyesters can also beused that include a phosphoester linkage that is a phosphite. Suitableterephthalate polyester-polyphosphite copolymers are described, forexample, in U.S. Pat. No. 6,419,709 (Mao et al., “BiodegradableTerephthalate Polyester-Poly(Phosphite) Compositions, Articles, andMethods of Using the Same). Biodegradable terephthalate polyester canalso be used that include a phosphoester linkage that is a phosphonate.Suitable terephthalate polyester-poly(phosphonate) copolymers aredescribed, for example, in U.S. Pat. Nos. 6,485,737 and 6,153,212 (Maoet al., “Biodegradable Terephthalate Polyester-Poly(Phosphonate)Compositions, Articles and Methods of Using the Same). Biodegradableterephthalate polyesters can be used that include a phosphoester linkagethat is a phosphate. Suitable terephthalate polyester-poly(phosphate)copolymers are described, for example, in U.S. Pat. Nos. 6,322,797 and6,600,010 (Mao et al., “Biodegradable TerephthalatePolyester-Poly(Phosphate) Polymers, Compositions, Articles, and Methodsfor Making and Using the Same).

Biodegradable polyhydric alcohol esters can also be used (See U.S. Pat.No. 6,592,895). This patent describes biodegradable star-shaped polymersthat are made by esterifying polyhydric alcohols to provide acylmoieties originating from aliphatic homopolymer or copolymer polyesters.The biodegradable polymer can be a three-dimensional crosslinked polymernetwork containing hydrophobic and hydrophilic components which forms ahydrogel with a crosslinked polymer structure, such as that described inU.S. Pat. No. 6,583,219. The hydrophobic component is a hydrophobicmacromer with unsaturated group terminated ends, and the hydrophilicpolymer is a polysaccharide containing hydroxy groups that are reactedwith unsaturated group introducing compounds. The components areconvertible into a one-phase crosslinked polymer network structure byfree radical polymerization. In yet further embodiments, thebiodegradable polymer can comprise a polymer based upon α-amino acids(such as elastomeric copolyester amides or copolyester urethanes, asdescribed in U.S. Pat. No. 6,503,538).

The biodegradable microparticle can include one or more biodegradablepolymers obtained from natural sources. In some preferred aspects thebiodegradable polymer is selected from hyaluronic acid, dextran, starch,amylose, amylopectin, cellulose, xanthan, pullulan, chitosan, pectin,inulin, alginates, and heparin. One, or combinations of more than one ofthese biodegradable polymers, can be used. A particular biodegradablepolymer can also be selected based on the type of bioactive agent thatis present in the microparticle. Therefore, in some aspects of theinvention, the biodegradable coating can include a natural biodegradablepolysaccharide matrix and a natural biodegradablepolysaccharide-containing microparticle.

Therefore, in some embodiments, the microparticles include a naturalbiodegradable polysaccharide such as amylose or maltodextrin. In someembodiments the natural biodegradable polysaccharide can be the primarybiodegradable component in the microparticle. In some embodiments, boththe coating matrix and the microparticle include amylose and/ormaltodextrin as components.

Dextran-based microparticles can be particularly useful for theincorporation of bioactive agents such as proteins, peptides, andnucleic acids. Examples of the preparation of dextran-basedmicroparticles are described in U.S. Pat. No. 6,303,148.

The preparation of amylose and other starch-based microparticles havebeen described in various references, including, for example, U.S. Pat.No. 4,713,249; U.S. Pat. No. 6,692,770; and U.S. Pat. No. 6,703,048.Biodegradable polymers and their synthesis have been also been describedin various references including Mayer, J. M., and Kaplan, D. L. (1994)Trends in Polymer Science 2: pages 227-235; and Jagur-Grodzinski, J.,(1999) Reactive and Functional Polymers: Biomedical Application ofFunctional Polymers, Vol. 39, pages 99-138.

In some aspects of the invention, the biodegradable microparticlecontains a biologically active agent (a “bioactive agent”), such as apharmaceutical or a prodrug. Microparticles can be preparedincorporating various bioactive agents by established techniques, forexample, by solvent evaporation (see, for example, Wichert, B. andRohdewald, P. J. Microencapsul. (1993) 10:195). The bioactive agent canbe released from the biodegradable microparticle (the microparticlebeing present in the natural biodegradable polysaccharide coating) upondegradation of the biodegradable microparticle in vivo. Microparticleshaving bioactive agent can be formulated to release a desired amount ofthe agent over a predetermined period of time. It is understood thatfactors affecting the release of the bioactive agent and the amountreleased can be altered by the size of the microparticle, the amount ofbioactive agent incorporated into the microparticle, the type ofdegradable material used in fabricating the microparticle, the amount ofbiodegradable microparticles immobilized per unit area on the substrate,etc.

The microparticles can also be treated with a porogen, such as salt,sucrose, PEG, or an alcohol, to create pores of a desired size forincorporation of the bioactive agent.

The quantity of bioactive agents provided in the biodegradablemicroparticle can be adjusted by the user to achieve the desired effect.For example, a particular amount of anti-coagulant drug can beincorporated into the microparticle to provide a certain level ofanti-coagulant activity from the biodegradable coating. Biologicallyactive compounds can be provided by the microparticles in a rangesuitable for the application. In another example, protein molecules canbe provided by biodegradable microparticles. For example, the amount ofprotein molecules present can be in the range of 1-250,000 molecules per1 μm diameter microparticle.

Generally, the concentration of the bioactive agent present in thebiodegradable microparticles can be chosen based on any one or acombination of a number of factors, including, but not limited to, therelease rate from the coating, the type of bioactive agent(s) in thecoating, the desired local or systemic concentration of the bioactiveagent following release, and the half life of the bioactive agent. Insome cases the concentration of bioactive agent in the microparticle canbe about 0.001% or greater, or in the range of about 0.001% to about 50percent, or greater, by weight, based on the weight of themicroparticle.

The particular bioactive agent to be included in the biodegradablemicroparticle, or combination of bioactive agents in microparticles, canbe selected depending upon factors such as the application of the coateddevice, the medical condition to be treated, the anticipated duration oftreatment, characteristics of the implantation site, the number and typeof bioactive agents to be utilized, the chemical composition of themicroparticle, size of the microparticle, crosslinking, and the like.

In one embodiment, the invention advantageously allows for preparationof surfaces having two, or more than two, different bioactive agents,wherein the bioactive agents are mutually incompatible in a particularenvironment, for example, as hydrophobic and hydrophilic drugs areincompatible in either a polar or non-polar solvent. Different bioactiveagents may also demonstrate incompatibility based on protic/aproticsolvents or ionic/non-ionic solvents. For example, the invention allowsfor the preparation of one set of biodegradable microparticlescontaining a hydrophobic drug and the preparation of another set ofbiodegradable microparticles containing a hydrophilic drug; the mixingof the two different sets of microparticles into a polymeric materialused to form the matrix; and the disposing of the mixture on the surfaceof a substrate. Both hydrophobic and hydrophilic drugs can be releasedfrom the surface of the coated substrate at the same time as thebiodegradable microparticles degrade, or the composition of thebiodegradable microparticles or the natural biodegradable polysaccharidematrix can be altered so that one bioactive agent is released at adifferent rate or time than the other one.

Biodegradable microparticles can be prepared having compositions thatare suitable for either hydrophobic or hydrophilic drugs. For example,polymers such as polylactide or polycaprolactone can be useful forpreparing biodegradable microparticles that include hydrophobic drugs;whereas polymers such as amylose or glycolide can be useful forpreparing microparticles that include hydrophilic drugs.

Traditional coating procedures directed at disposing at least twodifferent types of bioactive agents have often required that thebioactive agents be put down separately. Traditional approaches mayinclude the steps of solubilizing a hydrophobic drug in a non-polarsolvent, coating the surface of the substrate with the non-polarmixture, drying the non-polar mixture, solubilizing the hydrophilic drugin a polar solvent, coating the layer of the dried non-polar mixturewith the polar mixture, and then drying the polar mixture. This type oftraditional coating process can be inefficient and can also result inundesirable surface properties (e.g., the layering of the drugs willcause one drug to be released before the other one is released).According to this aspect of the invention, the method of preparingsurfaces having two, or more than two, different bioactive agents, inparticular when the two different bioactive agents are released from thesurface of the substrate, is a significant improvement over traditionalmethods of coating substrates and delivering bioactive agents from thesurface of the substrates.

Components of the biodegradable coating can be applied to the medicaldevice using standard techniques to cover the entire surface of thedevice, or a portion of the device surface. As indicated, the componentscan be applied to the medical device independently or together, forexample, in a composition. The coating formed on the device can be asingle layer coating, or a multiple layer coating.

Various factors can influence the delivery of bioactive agents from thecoating. These include the concentration of the natural biodegradablepolysaccharide and the extent of natural biodegradable polysaccharidecoupling in the coating, the amount and location of biodegradablemicroparticles associated with the coating, the concentration ofbioactive agent in the microparticles, and the presence of other coatedlayers, if included in the overall coating and the like. For example,the rate of delivery of the drug can be decreased by increasing theconcentration of polymeric material or the relative amount of couplingor crosslinking of the polymeric material in the polymeric matrix or inthe microparticle. Based on the description provided herein and thegeneral knowledge in this technical area, one can alter properties ofthe coating to provide a desired release rate for one or more particularbioactive agents from the coating.

Portions of the coating can be prepared to degrade at the same ordifferent rates. For example, the biodegradable microparticles can beprepared or obtained to have a faster rate of degradation than thenatural biodegradable polysaccharide matrix. In this case, the bioactiveagent can be released into the natural biodegradable polysaccharidematrix and/or diffuse out of the natural biodegradable polysaccharidematrix.

A natural biodegradable polysaccharide-based coating can be prepared byany one of a variety of methods. A “coating” as used herein can includeone or more “coated layers”, each coated layer including one or morecoating materials. In many cases, the coating consists of a single layerof material that includes the natural biodegradable polysaccharide, suchas amylose or maltodextrin. In other cases, the coating includes morethan one coated layer, at least one of the coated layers including thenatural biodegradable polysaccharide. If more than one layer is presentin the coating, the layers can be composed of the same or differentmaterials. If multiple polymeric layers are provided on the surface,each individual layer of polymer can be chosen to provide a desiredeffect. Additionally, multiple layers of various bioactive agents can bedeposited onto the medical device surface so that a particular bioactiveagent can be presented to or released from the medical device at onetime, one or more bioactive agents in each layer, which can be separatedby polymeric material.

If more than one coated layer is applied to a surface, it is typicallyapplied successively. For example, a natural biodegradablepolysaccharide coated layer can be formed by, for example, dipping,spraying, bushing, or swabbing the coating material on the article toform a layer, and then drying the coated layer. The process can berepeated to provide a coating having multiple coated layers, wherein atleast one layer includes the natural biodegradable polysaccharide.

Thus, in some embodiments wherein multiple coated layers are prepared,each coated layer is composed of the same materials. Alternatively, oneor more of the coated layers is composed of materials that are differentfrom one or more of the other layers. Additionally, multiple layers ofvarious bioactive agents can be deposited onto the medical articlesurface so that a particular bioactive agent can be presented to orreleased from the medical article at one time, one or more bioactiveagents in each layer, which can be separated by polymeric material.

The invention also provides the advantage of maintaining excellentcontrol over the formation of a coating on the surface of an article. Toexemplify this aspect of the invention, an initiator is disposed on asurface of a medical article along with the natural biodegradablepolysaccharide having pendent coupling groups. A bioactive agent can bedisposed if desired. The initiator can be disposed in a mixture with thenatural biodegradable polysaccharide together, or the initiator can bedisposed independently. These compounds are generally disposed in afluid state (for example, suspended or dissolved in an aqueous liquid)and can be disposed on an article surface using any one of number oftechniques as described herein. After the initiator and naturalbiodegradable polysaccharide are both disposed, the initiator isactivated, resulting in the activation of the pendent coupling groups,the coupling of natural biodegradable polysaccharide molecules, and theformation of the coating. The steps of disposing and activating can beperformed in ways (as described herein and/or known in the art) toprecisely control the formation of a coating. For example, the thicknessand the location of the coating on the article surface can be controlledusing techniques described herein and/or known in the art.

In preferred aspects of the following methods, the natural biodegradablepolysaccharide is selected from the group of amylose and maltodextrin.In other preferred aspects of the following methods, the naturalbiodegradable polysaccharide has a molecular weight of 500,000 Da orless, 250,000 Da or less, 100,000 Da or less, or 50,000 Da or less. Itis also preferred that the natural biodegradable polysaccharides have anaverage molecular weight of 500 Da or greater. A particularly preferredsize range for the natural biodegradable polysaccharides is in the rangeof about 1000 Da to about 10,000 Da.

For example, in some aspects the method includes the steps of (i)disposing a composition comprising (a) a natural biodegradablepolysaccharide having a coupling group, (b) an initiator, and (c) abioactive agent on a surface; and (ii) activating the initiator toprovide a coated composition having the natural biodegradablepolysaccharide and the bioactive agent on the surface. This method canalso be used to form a medical implant wherein the composition isdisposed to form an implant of a desired configuration. For example, thecomposition can be disposed in a mold. This method can also be used toform an in situ formed matrix wherein the composition is disposed withina portion of a subject.

In other aspects, the method includes the steps of (i) disposing aninitiator on a surface, (ii) disposing a composition comprising (a) anatural biodegradable polysaccharide having a coupling group and (b) abioactive agent on the surface; and (iii) activating the initiator toprovide a coated composition having the natural biodegradablepolysaccharide and the bioactive agent.

During the step of activating, a composition including the naturalbiodegradable polysaccharide and the bioactive agent are contacted withthe initiator and the initiator is activated to promote the crosslinkingof two or more natural biodegradable polysaccharides via their couplinggroups. In preferred aspects the natural biodegradable polysaccharideincludes a polymerizable group, such as an ethylenically unsaturatedgroup, and initiator is capable of initiating free radicalpolymerization of the polymerizable groups. Therefore, in anotherembodiment, the invention provides a method for coating a surface,including the steps of (i) disposing a composition comprising (a) anatural biodegradable polysaccharide having a ethylenically unsaturatedgroup, (b) a polymerization initiator, and (c) a bioactive agent on asurface; and (ii) activating the polymerization initiator to cause thepolymerization of the amylose compound thereby providing a coatedcomposition having the natural biodegradable polysaccharide and thebioactive agent on the surface. These methods can also be used to formmedical implants and in situ-formed matrices, wherein the composition isdisposed in a mold or in a subject, respectively, rather than on asurface.

In yet another aspect the invention provides a medical device having acoated composition comprising a plurality of coupled naturalbiodegradable polysaccharide and a bioactive agent.

In some embodiments, the invention provides methods for preparingbiodegradable coatings that include (a) a natural biodegradablepolysaccharide having a coupling group and (b) biodegradablemicroparticles having a bioactive agent.

In some embodiments the coupling group can be activated by an initiator.Therefore, the method can include the steps of (i) disposing aninitiator on a surface, (ii) disposing a composition comprising (a) anatural biodegradable polysaccharide having a coupling group and (b)biodegradable microparticles comprising a bioactive agent; and (iii)activating the initiator to provide a biodegradable bioactiveagent-releasing coated composition having the natural biodegradablepolysaccharide and the biodegradable microparticles having the bioactiveagent.

In preferred aspects the natural biodegradable polysaccharide includes apolymerizable group, such as an ethylenically unsaturated group, andinitiator is capable of initiating free radical polymerization of thepolymerizable groups. Therefore, in another embodiment, the inventionprovides a method for coating a surface, including the steps of (i)disposing a composition comprising (a) a natural biodegradablepolysaccharide having an ethylenically unsaturated group, (b) apolymerization initiator, and (c) biodegradable microparticles having abioactive agent on a surface; and (ii) activating the polymerizationinitiator to cause the polymerization of the natural biodegradablepolysaccharide thereby providing a coated composition that includesbiodegradable microparticles in a natural biodegradable polysaccharidematrix. The invention also provides alternative methods for preparing acoated surface that is biodegradable and having microparticles that canrelease a bioactive agent. The methods include disposing in two or moresteps at least the following reagents on a surface: (a) a naturalbiodegradable polysaccharide comprising a first coupling group (b) anatural biodegradable polysaccharide comprising a second coupling groupthat is reactive with the first coupling group, and (c) biodegradablemicroparticles that include a bioactive agent. According to this methodreagents (a) and (b) are reactive with each other and are disposedseparately on the surface but can individually include (c). For example,reagent (a) is first disposed on the surface and then a mixturecomprising reagent (b) and (c) is then disposed on reagent (a). Reagent(a) reacts with (b) to link the natural biodegradable polysaccharidetogether to form a coating that includes (c), the biodegradablemicroparticles.

The invention also provides methods for preparing biodegradable sealantcoatings that include a natural biodegradable polysaccharide having acoupling group; optionally a bioactive agent can be included in thesealant coating.

In some embodiments, the method includes the steps of (i) disposing asealant composition comprising (a) a natural biodegradablepolysaccharide having a coupling group, and (b) an initiator, and (ii)activating the initiator to form a sealant coating. This aspect of theinvention includes coating methods where a bulk polymerization approachis performed. For example, in some embodiments, a composition includinga polymerization initiator and natural biodegradable polysaccharideshaving a polymerizable group is disposed on a surface. The initiator isthen activated to promote bulk polymerization and coupling of thenatural biodegradable polysaccharides in association with the surface.

In other aspects, the method includes the steps of (i) disposing aninitiator on a surface, (ii) disposing a natural biodegradablepolysaccharide having a coupling group; and (iii) activating theinitiator to provide a coated composition having the amylose polymer.The natural biodegradable polysaccharides can be disposed on the surfacealong with other reagents if desired. This aspect of the inventionincludes coating methods where a graft polymerization approach isperformed. For example, in some embodiments, a polymerization initiatoris first disposed on a surface and then a natural biodegradablepolysaccharide having a polymerizable group is disposed on the surfacehaving the initiator. The initiator is activated to promote free radicalpolymerization, and coupling of the natural biodegradablepolysaccharides from the surface.

In other embodiments of the invention, an aqueous composition thatincludes the natural biodegradable polysaccharide having the couplinggroup and a bioactive agent is obtained and used in the method ofproviding a sealant coating to a surface. This composition can beprepared by mixing the natural biodegradable polysaccharide with abioactive agent, for example, a water-soluble small molecule, a protein,or a nucleic acid. In one preferred aspect of the invention, thebioactive agent is a procoagulant or prothrombotic factor. For example,the bioactive agent can be a protein such as recombinant collagen, orother proteins that associate with receptors on platelets to induceplatelet aggregation.

In some aspects of the invention, the coating is placed in contact withan aqueous solution, or the materials of the coating composition. Thecoating or coating materials are designed to be stable in the presenceof the aqueous solution provided that an enzyme that causes thedegradation of the natural biodegradable polysaccharide (or anotherdegrading agent) is not present in an amount sufficient to causesubstantial degradation of the materials.

For example, the invention provides a shelf stable compositioncomprising a natural biodegradable polysaccharide comprising couplinggroups. These compositions could be obtained or prepared, according tothe details provided herein, and then stored for a period of time beforethe composition is used to form a biodegradable coating, without thesignificant degradation of the natural biodegradable polysaccharideoccurring during storage.

Accordingly, the invention also provides methods for preparing abiodegradable coating comprising preparing a biodegradable coatingcomposition comprising a natural biodegradable polysaccharide comprisingcoupling group; storing the coating composition for an amount of time;and then using the coating composition to prepare a biodegradablecoating. Optionally, one or more bioactive agents and/or microparticlescan be added before or after storage of the coating composition.

In a related aspect, the invention also provides the advantage of beingable to perform synthetic and post-synthetic procedures wherein thenatural biodegradable polysaccharide is contacted with an aqueouscomposition, and there is minimal risk of degradation of thepolysaccharide. For example, the natural biodegradable polysaccharidemay be contacted with an aqueous solution for purification withoutrisking significant degradation of the natural biodegradablepolysaccharide.

In yet another aspect, the invention relates to the stability of thecoatings that are formed on an article. The invention provides a methodcomprising obtaining an article having a coating comprising a naturalbiodegradable polysaccharide, and then contacting the article with anaqueous solution. The aqueous solution can be, for example, a storagesolution, a solution that is used to hydrate the surface of the coateddevice, or an aqueous sterilization solution.

In some aspects the coating can be contacted with an aqueoussterilization solution. Medical articles, or parts of medical articles,can be prepared having a coating and these articles can be treated tosterilize one or more parts of the article, or the entire medicalarticle. Sterilization can take place prior to using the medical articleand/or, in some cases, during implantation of the medical article.

In some aspects, the invention provides a method for delivering abioactive agent from a biodegradable coating or a biodegradable articleby exposing the coating or article to an enzyme that causes thedegradation of the coating. In performing this method a coated article,such as an implantable medical device is provided to a subject. Thecoated article has a biodegradable coating comprising a naturalbiodegradable polysaccharide having pendent coupling groups, wherein thecoating is formed on a surface of the article by reaction of thecoupling groups to form a crosslinked matrix of a plurality of naturalbiodegradable polysaccharides, and wherein the coating includes abioactive agent. The coating or article is then exposed to acarbohydrase that can promote the degradation of the biodegradablecoating.

The carbohydrase that contacts the coating or article can specificallydegrade the natural biodegradable polysaccharide causing release of thebioactive agent. Examples of carbohydrases that can specifically degradenatural biodegradable polysaccharide coatings include α-amylases, suchas salivary and pancreatic α-amylases; disaccharidases, such as maltase,lactase and sucrase; trisaccharidases; and glucoamylase(amyloglucosidase).

Serum concentrations for amylase are estimated to be in the range ofabout 50-100 U per liter, and vitreal concentrations also fall withinthis range (Varela, R. A., and Bossart, G. D. (2005) J Am Vet Med Assoc226:88-92).

In some aspects, the carbohydrase can be administered to a subject toincrease the local concentration, for example in the serum or the tissuesurrounding the implanted device, so that the carbohydrase may promotethe degradation of the coating. Exemplary routes for introducing acarbohydrase include local injection, intravenous (IV) routes, and thelike. Alternatively, degradation can be promoted by indirectlyincreasing the concentration of a carbohydrase in the vicinity of thecoated article, for example, by a dietary process, or by ingesting oradministering a compound that increases the systemic levels of acarbohydrase.

In other cases, the carbohydrase can be provided on a portion of thecoated article. For example the carbohydrase may be eluted from aportion of the article that does not have the natural biodegradablepolymer coating. In this aspect, as the carbohydrase is released itlocally acts upon the coating to cause its degradation and promote therelease of the bioactive agent. Alternatively, the carbohydrase can bepresent in a microparticle in one or more portions the coating. As thecarbohydrase is released from the microparticle, it causes coatingdegradation and promote the release of the bioactive agent.

In another aspect, the invention sets forth methods for providinglubricity to an article surface. The matrix of biodegradablepolysaccharides as described herein can provide a surprisinglylubricious and durable surface when formed, for example, on the surfaceof a device.

As used herein, the term “lubricity” refers to a characterization of thefrictional force associated with a coating. A lubricious coating canreduce the frictional forces present on the surface of the device whenanother surface is moved against the device surface. For example, acatheter having a coating that provides improved lubricity willencounter less frictional resistance when moved within a portion of thebody, as compared to an uncoated substrate, or a coating that is notlubricious. Lubricity can also be important for devices with innermoving parts in addition to devices that function along with anotherdevice, for example, a coronary catheter which guides the insertion of aPTCA catheter. The methods can be used to prepare lubricious coatingsfor short term use and/or single use devices.

Improved lubricity can be shown by one or more methods. One method oftesting lubricity of a coating is by the horizontal sled style frictiontest method (such as ASTM D-1894; a modified test is described herein).The lubricity measurements described herein refer to the kineticcoefficient of friction, which is equal to the average force readingobtained during uniform sliding of the surfaces divided by the sledweight. The measurements are in grams.

As shown herein, the biodegradable polysaccharide coatings generallyshow a lubricity of 20 g or less, and coatings having a lubricity of 15g or less, or 10 g or less can be prepared by the methods describedherein. In one desirable method for preparing the coating, abiodegradable polysaccharide matrix is formed using a photoinitiator topromote association of the biodegradable polysaccharides and matrixformation.

Another method which can be used to demonstrate an improvement inlubricity is the water contact angle measurement method. Reduction ofwater contact angle is indicative of increased wettability, whichassociates with an improvement in lubricity.

Also, in many aspects, the biodegradable coating of the inventiondemonstrates excellent durability. As used herein, the term “durability”refers to the wear resistance of the biodegradable polysaccharidecoating. A more durable coating is less easily removed from a substrateby abrasion. Durability of a coating can be assessed by subjecting thedevice to conditions that simulate use conditions. The durability of thecoating compositions is demonstrated by the ability to adhere to thedevice surface sufficiently to withstand the effect of shear forcesencountered during insertion and/or removal of the device, which couldotherwise result in delamination of the coating from the body member.

Improved durability can be shown by one or more methods. One preferredmethod of testing durability, as well as lubricity, is by the horizontalsled style friction test method described herein. In the method multiplepush-pull cycles are performed and friction measurements are takenduring the measurements. If minimal increase in friction values is seenafter multiple push pull cycles, the coating is though to have gooddurability.

The biodegradable coatings of the present invention showed excellentdurability. For example, the lubricity of the fifth push and pull cyclegenerally was not greater than 10% or more typically not greater than 5%of the lubricity of the first push and pull cycle. At later points, forexample, at the fortieth push and pull cycle, the lubricity generallywas not greater than 20% or more typically not greater than 10% of thelubricity of the first push and pull cycle.

The invention will be further described with reference to the followingnon-limiting Examples. It will be apparent to those skilled in the artthat many changes can be made in the embodiments described withoutdeparting from the scope of the present invention. Thus the scope of thepresent invention should not be limited to the embodiments described inthis application, but only by embodiments described by the language ofthe claims and the equivalents of those embodiments. Unless otherwiseindicated, all percentages are by weight.

EXAMPLE 1 Synthesis of Acrylated-Amylose

Amylose having polymerizable vinyl groups was prepared by mixing 0.75 gof amylose (A0512; Aldrich) with 100 mL of methylsulfoxide (JT Baker) ina 250 mL amber vial, with stirring. After one hour, 2 mL oftriethylamine (TEA; Aldrich) was added and the mixture was allowed tostir for 5 minutes at room temperature. Subsequently, 2 mL of glycidylacrylate (Polysciences) was added and the amylose and glycidyl acrylatewere allowed to react by stirring overnight at room temperature. Themixture containing the amylose-glycidyl acrylate reaction product wasdialyzed for 3 days against DI water using continuous flow dialysis. Theresultant acrylated-amylose (0.50 g; 71.4% yield) was then lyophilizedand stored desiccated at room temperature with protection from light.

EXAMPLE 2 Synthesis of MTA-PAAm

A polymerization initiator was prepared by copolymerizing amethacrylamide having a photoreactive group with acrylamide.

A methacrylamide-oxothioxanthene monomer(N-[3-(7-Methyl-9-oxothioxanthene-3-carboxamido)propyl]methacrylamide(MTA-APMA)) was first prepared. N-(3-aminopropyl)methacrylamidehydrochloride (APMA), 4.53 g (25.4 mmol), prepared as described in U.S.Pat. No. 5,858,653, Example 2, was suspended in 100 mL of anhydrouschloroform in a 250 mL round bottom flask equipped with a drying tube.7-methyl-9-oxothioxanthene-3-carboxylic acid (MTA) was prepared asdescribed in U.S. Pat. No. 4,506,083, Example D. MTA-chloride (MTA-Cl)was made as described in U.S. Pat. No. 6,007,833, Example 1. Aftercooling the slurry in an ice bath, MTA-Cl (7.69 g; 26.6 mmol) was addedas a solid with stirring to the APMA-chloroform suspension. A solutionof 7.42 mL (53.2 mmol) of TEA in 20 mL of chloroform was then added overa 1.5 hour time period, followed by a slow warming to room temperature.The mixture was allowed to stir 16 hours at room temperature under adrying tube. After this time, the reaction was washed with 0.1 N HCl andthe solvent was removed under vacuum after adding a small amount ofphenothiazine as an inhibitor. The resulting product was recrystallizedfrom tetrahydrofuran (THF)/toluene (3/1) and gave 8.87 g (88.7% yield)of product after air drying. The structure of MTA-APMA was confirmed byNMR analysis.

MTA-APMA was then copolymerized with acrylamide in DMSO in the presenceof 2-mercaptoethanol (a chain transfer agent),N,N,N′,N′-tetramethyl-ethylenediamine (a co-catalyst), and2,2′-azobis(2-methyl-propionitrile) (a free radical initiator) at roomtemperature. The solution was sparged with nitrogen for 20 minutes,sealed tightly, and incubated at 55° C. for 20 hours. The solution wasdialyzed for 3 days against DI water using continuous flow dialysis. Theresultant MTA-PAAm was lyophilized, stored desiccated, and protectedfrom light at room temperature.

EXAMPLE 3 Formation of an Amylose Coating

100 mg of acrylated-amylose as prepared in Example 1 was placed in an 8mL amber vial. To the acrylated-amylose was added 3 mg of MTA-PAAm(lyophilized), 2 μL of 2-NVP (N-vinyl-2-pyrrolidone; accelerant (Bimax))and 1 mL of 1× phosphate-buffered saline (1×PBS). The reagents were thenmixed for one hour on a shaker at 37° C. The mixture in an amount of 50μL was placed onto a glass slide (2991FI; Esco) and illuminated for 50seconds with an EFOS 100 SS illumination system equipped with a 400-500nm filter (50 mW/cm²). After illumination the polymer was found to forma semi-firm gel having elastomeric properties.

EXAMPLE 4 Preparation of 4-bromomethylbenzophenone (BMBP)

4-Methylbenzophenone (750 g; 3.82 moles) was added to a 5 liter Mortonflask equipped with an overhead stirrer and dissolved in 2850 mL ofbenzene. The solution was then heated to reflux, followed by thedropwise addition of 610 g (3.82 moles) of bromine in 330 mL of benzene.The addition rate was approximately 1.5 mL/min and the flask wasilluminated with a 90 watt (90 joule/sec) halogen spotlight to initiatethe reaction. A timer was used with the lamp to provide a 10% duty cycle(on 5 seconds, off 40 seconds), followed in one hour by a 20% duty cycle(on 10 seconds, off 40 seconds). At the end of the addition, the productwas analyzed by gas chromatography and was found to contain 71% of thedesired 4-bromomethylbenzophenone, 8% of the dibromo product, and 20%unreacted 4-methylbenzophenone. After cooling, the reaction mixture waswashed with 10 g of sodium bisulfite in 100 mL of water, followed bywashing with 3×200 mL of water. The product was dried over sodiumsulfate and recrystallized twice from 1:3 toluene:hexane. After dryingunder vacuum, 635 g of 4-bromomethylbenzophenone was isolated, providinga yield of 60%, having a melting point of 112° C.-114° C. Nuclearmagnetic resonance (“NMR”) analysis (¹H NMR (CDCl₃)) was consistent withthe desired product: aromatic protons 7.20-7.80 (m, 9H) and methyleneprotons 4.48 (s, 2H). All chemical shift values are in ppm downfieldfrom a tetramethylsilane internal standard.

EXAMPLE 5 Preparation of ethylenebis(4-benzoylbenzyldimethylammonium)dibromide

N,N,N′,N′-Tetramethylethylenediamine (6 g; 51.7 mmol) was dissolved in225 mL of chloroform with stirring. BMBP (29.15 g; 106.0 mmol), asdescribed in Example 4, was added as a solid and the reaction mixturewas stirred at room temperature for 72 hours. After this time, theresulting solid was isolated by filtration and the white solid wasrinsed with cold chloroform. The residual solvent was removed undervacuum and 34.4 g of solid was isolated for a 99.7% yield, melting point218° C.-220° C. Analysis on an NMR spectrometer was consistent with thedesired product: ¹H NMR (DMSO-d₆) aromatic protons 7.20-7.80 (m, 18H),benzylic methylenes 4.80 (br. s, 4H), amine methylenes 4.15 (br. s, 4H),and methyls 3.15 (br. s, 12H).

EXAMPLE 6 Formation of an Amylose Matrix on PET Mesh

Acrylated-amylose (100 mg), as described in Example 1, was placed in an8 mL amber vial. Ethylenebis(4-benzoylbenzyldimethylammonium) dibromide(3 mg), as described in Example 5, 2 μl of 2-NVP, and 1 mL of 1×phosphate buffered saline (1×PBS) was added to the acrylated-amylose andmixed for two hours on a shaker at 37° C. The mixture (250 μl) wasspread onto a 3 cm×2 cm polyethylene terephthalate (PET) mesh substrate(41 μm monofil diameter; Goodfellow Cambridge Ltd., UK). The PETsubstrate with the applied amylose mixture was placed in a DymaxLightweld PC-2 illumination system (Dymax Corp.; light intensity 6.5mW/cm²), 15 cm from the light source, and illuminated for 60 seconds.After illumination, the applied amylose mixture was found to form asemi-firm gel on the PET substrate, with elastomeric properties evident.

EXAMPLE 7 Preparation of 1-(6-oxo-6-hydroxyhexyl)maleimide (Mal-EACA)

A maleimide functional acid was prepared in the following manner, andwas used in Example 8. EACA (6-aminocaproic acid), (100 g; 0.762 moles),was dissolved in 300 mL of acetic acid in a three-neck, three literflask equipped with an overhead stirrer and drying tube. Maleicanhydride, (78.5 g; 0.801 moles), was dissolved in 200 mL of acetic acidand added to the EACA solution. The mixture was stirred one hour whileheating on a boiling water bath, resulting in the formation of a whitesolid. After cooling overnight at room temperature, the solid wascollected by filtration and rinsed two times with 50 mL of hexane eachrinse. After drying, the yield of the (z)-4-oxo-5-aza-undec-2-endioicacid (Compound 1) was in the range of 158-165 g (90-95%) with a meltingpoint of 160-165° C. Analysis on an NMR spectrometer was consistent withthe desired product: ¹H NMR (DMSO-d₆, 400 MHz) δ 6.41, 6.24 (d, 2H,J=12.6 Hz; vinyl protons), 3.6-3.2 (b, 1H; amide proton), 3.20-3.14 (m,2H: methylene adjacent to nitrogen), 2.20 (t, 2H, J=7.3; methyleneadjacent to carbonyl), 1.53-1.44 (m, 4H; methylenes adjacent to thecentral methylene), and 1.32-1.26 (m, 2H; the central methylene).

(z)-4-oxo-5-aza-undec-2-endioic acid, (160 g; 0.698 moles), zincchloride, 280 g (2.05 moles), and phenothiazine, 0.15 g were added to atwo liter round bottom flask fitted with an overhead stirrer, condenser,thermocouple, addition funnel, an inert gas inlet, and heating mantle.Chloroform (CHCl₃), 320 mL was added to the 2 liter reaction flask, andstirring of the mixture was started. Triethylamine (480 mL; 348 g, 3.44moles (TEA)) was added over one hour. Chlorotrimethyl silane (600 mL;510 g, 4.69 moles) was then added over two hours. The reaction wasbrought to reflux and was refluxed overnight (˜16 hours). The reactionwas cooled and added to a mixture of CHCl₃ (500 mL), water (1.0 liters),ice (300 g), and 12 N hydrochloric acid (240 mL) in a 20 liter containerover 15 minutes. After 15 minutes of stirring, the aqueous layer wastested to make sure the pH was less than 5. The organic layer wasseparated, and the aqueous layer was extracted three times with CHCl₃(700 mL) each extraction. The organic layers were combined andevaporated on a rotary evaporator. The residue was then placed in a 20liter container. A solution of sodium bicarbonate (192 g) in water (2.4liters) was added to the residue. The bicarbonate solution was stirreduntil the solids were dissolved. The bicarbonate solution was treatedwith a solution of hydrochloric acid, (26 liters of 1.1 N) over 5minutes to a pH of below 2. The acidified mixture was then extractedwith two portions of CHCl₃, (1.2 liters and 0.8 liters) each extraction.The combined extracts were dried over sodium sulfate and evaporated. Theresidue was recrystallized from toluene and hexane. The crystallineproduct was then isolated by filtration and dried which produced 85.6 gof white N-(6-oxo-6-hydroxyhexyl)maleimide (Mal-EACA; Compound 2).Analysis on an NMR spectrometer was consistent with the desired product:¹H NMR (CDCl₃, 400 MHz) δ 6.72 (s, 2H; maleimide protons), 3.52 (t, 2H,J=7.2 Hz; methylene next to maleimide), 2.35 (t, 2H, J=7.4; methylenenext to carbonyl), 1.69-1.57 (m, 4H; methylenes adjacent to centralmethylene), and 1.39-1.30 (m, 2H; the central methylene). The producthad a DSC (differential scanning calorimator) melting point peak at89.9⁰ C.

EXAMPLE 8 Preparation of N-(5-isocyanatopentyl)maleimide (Mal-C5-NCO)

Mal-EACA from Example 7 (5.0 g; 23.5 mmole) and CHCl₃ (25 mL) wereplaced in a 100 mL round bottom flask and stirred using a magnetic barwith cooling in an ice bath. Oxalyl chloride (10.3 mL; ˜15 g; 118 mmole)was added and the reaction was brought to room temperature with stirringovernight. The volatiles were removed on a rotary evaporator, and theresidue was azetroped with three times with 10 mL CHCl₃ each time. Theintermediate Mal-EAC-Cl [N-(6-oxo-6-chlorohexyl)maleimide] (Compound 3)was dissolved in acetone (10 mL) and added to a cold (ice bath) stirredsolution of sodium azide (2.23 g; 34.3 mmole) in water (10 mL). Themixture was stirred one hour using an ice bath. The organic layer wasset aside in an ice bath, and the aqueous layer was extracted threetimes with 10 mL CHCl₃. All operations of the acylazide were done at icebath temperatures. The combined organic solutions of the azide reactionwere dried for an hour over anhydrous sodium sulfate. TheN-(6-oxo-6-azidohexyl)maleimide (Compound 4) solution was further driedby gentle swirling over molecular sieves over night. The cold azidesolution was filtered and added to refluxing CHCl₃, 5 mL over a 10minute period. The azide solution was refluxed for 2 hours. The weightof Mal-C5-NCO (Compound 5) solution obtained was 55.5 g, which wasprotected from moisture. A sample of the isocyanate solution, 136 mg wasevaporated and treated with DBB (1,4-dibromobenzene), 7.54 mg andchloroform-d, 0.9 mL: ¹H NMR (CDCl₃, 400 MHz) δ 6.72 (s,2H), 3.55 (t,2H, J=7.2 Hz), 3.32 (t, 2H, J=6.6 Hz), 1.70-1.59 (m, 4H), 1.44-1.35 (m,2H). The NMR spectra was consistent with desired product. The DBBinternal standard 6 at 7.38 (integral value was 2.0, 4H; per mole ofproduct) was used to estimate the moles of Mal-C5-NCO in solution. Thecalculated amount of product in solution was 23.2 mmole for a yield of98% of theory. NCO reagent (concentration was 0.42 mmole/g) was used toprepare a macromer in Example 14.

EXAMPLE 9 Preparation of 3-(acryloyloxy)propanoic acid (2-carboxyethylacrylate; CEA)

Acrylic acid (100 g; 1.39 mole) and phenothiazine (0.1 g) were placed ina 500 mL round bottom flask. The reaction was stirred at 92⁰ C. for 14hours. The excess acrylic acid was removed on a rotary evaporator at 25⁰C. using a mechanical vacuum pump. The amount of residue obtained was51.3 g. The CEA (Compound 6) was used in Example 10 withoutpurification.

EXAMPLE 10 Preparation of 3-chloro-3-oxopropyl acrylate (CEA-Cl)

CEA from Example 9 (51 g; ˜0.35 mole) and dimethyl formamide (DMF; 0.2mL; 0.26 mmole) were dissolved in CH₂Cl₃ (100 mL). The CEA solution wasadded slowly (over 2 hours) to a stirred solution of oxalyl chloride (53mL; 0.61 mole), DMF (0.2 mL; 2.6 mmole), anthraquinone (0.5 g; 2.4mmole), phenothiazine (0.1 g, 0.5 mmole), and CH₂Cl₃ (75 mL) in a 500 mLround bottom flask in an ice bath at 200 mm pressure. A dry icecondenser was used to retain the CH₂Cl₃ in the reaction flask. After theaddition was complete the reaction was stirred at room temperatureovernight. The weight of reaction solution was 369 g. A sample of theCEA-Cl (Compound 7) reaction solution (124 mg) was treated with1,4-dibromobenzene (DBB, 6.85 mg) evaporated and dissolved in CDCl₃: ¹HNMR (CDCl₃, 400 MHz) δ 7.38 (s, 4H; DBB internal std.), 6.45 (d, 1H,J=17.4 Hz), 6.13 (dd, 1H, J=17.4, 10.4 Hz), 5.90 (d, 1H, J=10.4 Hz),4.47 (t, 2H, J=5.9 Hz), 3.28 (t, 2H, J=5.9). The spectra was consistentwith the desired product. There was 0.394 mole DBB for 1.0 mole CEA-Clby integration, which gave a calculated yield of 61%. Commerciallyavailable CEA (426 g; Aldrich) was reacted with oxalyl chloride (532 mL)in a procedure similar to the one listed above. The residue CEA-Cl (490g) was distilled using an oil bath at 140⁰ C. at a pressure of 18 mm Hg.The distillate temperature reached 98⁰ C. and 150 g of distillate wascollected. The distillate was redistilled at 18 mm Hg at a maximum bathtemperature of 120⁰ C. The temperature range for the distillate was 30⁰C. to 70⁰ C. which gave 11 g of material. The distillate appeared to be3-chloro-3-oxopropyl 3-chloropropanoate. The residue of the seconddistillation (125 g; 26% of theory) was used in Example 11.

EXAMPLE 11 Preparation of 3-azido-3-oxopropyl acrylate (CEA-N3)

CEA-Cl from Example 10 (109.2 g; 0.671 mole) was dissolved in acetone(135 mL). Sodium azide (57.2 g; 0.806 mole) was dissolved in water (135mL) and chilled. The CEA-Cl solution was then added to the chilled azidesolution with vigorous stirring in an ice bath for 1.5 hours. Thereaction mixture was extracted two times with 150 mL of CHCl₃ eachextraction. The CHCl₃ solution was passed through a silica gel column 40mm in diameter by 127 mm. The 3-azido-3-oxopropyl acrylate (Compound 8)solution was gently agitated over dried molecular sieves at 4⁰ C.overnight. The dried solution was used in Example 12 withoutpurification.

EXAMPLE 12 Preparation of 2-isocyanatoethyl acrylate (EA-NCO)

The dried azide solution (from Example 11) was slowly added to refluxingCHCl₃, 75 mL. After the addition was completed, refluxing was continued2 hours. The EA-NCO (Compound 9) solution (594.3 g) was protected frommoisture. A sample of the EA-NCO solution (283.4 mg) was mixed with DBB(8.6 mg) and evaporated. The residue was dissolved in CDCl₃: ¹H NMR(CDCl₃, 400 MHz) δ 7.38 (s, 4H; DBB internal std.), 6.50 (d, 1H, J=17.3Hz), 6.19 (dd, 1H, J=17.3, 10.5 Hz), 5.93 (d, 1H, J=10.5 Hz), 4.32 (t,2H, J=5.3 Hz), 3.59 (t, 2H, J=5.3). The spectra was consistent with thedesired EA-NCO. There was 0.165 mole DBB for 1.0 mole EA-NCO byintegration, which gave a calculated concentration of 110 mg EA-NCO/g ofsolution. The EA-NCO solution was used to prepare a macromer in Example13.

EXAMPLE 13 Preparation of Maltodextrin-Acrylate Macromer (MD-Acrylate)

Maltodextrin (MD; Aldrich; 9.64 g; 3.21 mmole; DE (Dextrose Equivalent):4.0-7.0) was dissolved in dimethylsulfoxide (DMSO) 60 mL. The size ofthe maltodextrin was calculated to be in the range of 2,000 Da-4,000 Da.A solution of EA-NCO from Example 12 (24.73 g; 19.3 mmole) wasevaporated and dissolved in dried DMSO (7.5 mL). The two DMSO solutionswere mixed and heated to 55⁰ C. overnight. The DMSO solution was placedin dialysis tubing (1000 MWCO, 45 mm flat width×50 cm long) and dialyzedagainst water for 3 days. The macromer solution was filtered andlyophilized to give 7.91 g white solid. A sample of the macromer (49mg), and DBB (4.84 mg) was dissolved in 0.8 mL DMSO-d₆: ¹H NMR (DMSO-d₆,400 MHz) δ 7.38 (s, 4H; internal std. integral value of 2.7815), 6.50,6.19, and 5.93 (doublets, 3H; vinyl protons integral value of 3.0696).The calculated acrylate load of macromer was 0.616 μmoles/mg of polymer.

EXAMPLE 14 Preparation of Maltodextrin-Maleimide Macromer (MD-Mal)

A procedure similar to Example 13 was used to make the MD-Mal macromer.A solution of Mal-C5-NCO from Example 8 (0.412 g; 1.98 mmole) wasevaporated and dissolved in dried DMSO (2 mL). MD (0.991 g; 0.33 mmole)was dissolved in DMSO (5 mL). The DMSO solutions were combined andstirred at 55⁰ C. for 16 hours. Dialysis and lyophilization gave 0.566 gproduct. A sample of the macromer (44 mg), and DBB (2.74 mg) wasdissolved in 00.8 mL DMSO-d₆: ¹H NMR (DMSO-d₆, 400 MHz) δ 7.38 (s, 4H;internal std. integral value of 2.3832), 6.9 (s, 2H; Maleimide protonsintegral value of 1.000). The calculated acrylate load of macromer was0.222 μmoles/mg of polymer. The macromer was tested for its ability tomake a matrix (see Example 17)

EXAMPLE 15 Formation of Maltodextrin-Acrylate Biodegradable Matrix UsingMTA-PAAm

250 mg of MD-Acrylate as prepared in Example 13 was placed in an 8 mLamber vial. To the MD-Acrylate was added 3 mg of MTA-PAAm (lyophilized),2 μL of 2-NVP, and 1 mL of 1× phosphate-buffered saline (1×PBS),providing a composition having MD-Acrylate at 250 mg/mL. The reagentswere then mixed for one hour on a shaker at 37° C. The mixture in anamount of 50 μL was placed onto a glass slide and illuminated for 40seconds with an EFOS 100 SS illumination system equipped with a 400-500nm filter. After illumination the polymer was found to form a semi-firmgel having elastomeric properties.

EXAMPLE 16 Formation of MD-Acrylate Biodegradable Matrix UsingCamphorquinone

250 mg of MD-acrylate as prepared in Example 13 was placed in an 8 mLamber vial. To the MD-Acrylate was added 14 mg ofcamphorquinone-10-sulfonic acid hydrate (Toronto Research Chemicals,Inc.), 3 μL of 2-NVP, and 1 mL of distilled water. The reagents werethen mixed for one hour on a shaker at 37° C. The mixture in an amountof 50 μL was placed onto a glass slide and illuminated for 40 secondswith a SmartliteIQ™LED curing light (Dentsply Caulk). After illuminationthe polymer was found to form a semi-firm gel having with elastomericproperties.

EXAMPLE 17 Formation of MD-Mal Biodegradable Matrix Using MTA-PAAm

250 mg of MD-Mal as prepared in Example 14 was placed in an 8 mL ambervial. To the MD-Mal was added 3 mg of MTA-PAAm (lyophilized), 2 μL of2-NVP, and 1 mL of 1× phosphate-buffered saline (1×PBS). The reagentswere then mixed for one hour on a shaker at 37° C. The mixture in anamount of 50 μL was placed onto a glass slide and illuminated for 40seconds with an EFOS 100 SS illumination system equipped with a 400-500μm filter. After illumination the polymer was found to form a semi-firmgel having elastomeric properties.

EXAMPLE 18 Coating a PEBAX® Rod with MD-Acrylate

100 mg photo-derivatized poly(vinylpyrrolidone) (photo-PVP) as preparedas described in U.S. Pat. No. 5,637,460, and the photoinitiatortetrakis(4-benzoylbenzyl ether) of pentaerythritol [“tetra-BBE-PET”] (5mg), prepared as described in U.S. Pat. No. 5,414,075 (Example 1) andcommercially available from SurModics, Inc. (Eden Prairie, Minn.) asPR01, were mixed with 10 mL isopropyl alcohol (IPA; Fisher) for 1minute. The mixture in an amount of 1 mL was placed into a 1.8 mLeppendorf tube (VWR). A 1.2 cm PEBAX® rod (Medical Profiles, Inc) wasdipped into the solution for 10 seconds, at a dip rate of 0.1 cm/second,and then removed at the same rate. The rod was allowed to air dry for 5minutes. The rod was placed into a Dymax Lightweld PC-2 illuminationsystem (Dymax Corp.; light intensity 6.5 mW/cm²), 30 cm from lightsource, illuminated for 180 seconds, and then removed.

300 mg of MD-Acrylate, as prepared in Example 13, was placed in an 8 mLamber vial. To the MD-Acrylate was added4,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,3-disulfonic acid (5mg)(DBDS), prepared as described in U.S. Pat. No. 6,278,018 (Example 1)and commercially available from SurModics, Inc. (Eden Prairie, Minn.) asDBDS, and 1 mL of 1× phosphate-buffered saline (1×PBS). The reagentswere then mixed for one hour on a shaker at 37° C. The mixture in anamount of 1 mL was placed into a 1.8 mL eppendorf tube (VWR). Thephoto-PVP/tetra-BBE-PET coated PEBAX® rod was dipped into the mixturefor 30 seconds, at a dip rate of 0.3 cm/s, and then removed at the samerate. The rod was immediately placed into a Dymax Lightweld PC-2illumination system (Dymax Corp.; light intensity 6.5 mW/cm²), 30 cmfrom light source, and illuminated for 180 seconds and then removed.

The MD-Acrylate coated rod was examined under Scanning ElectronMicroscope (SEM; LEO Supra 35 VP); the MD-Acrylate coating thicknessvaried from 2.1 μm to 2.5 μm, with an average coating thickness of 2.3μm.

EXAMPLE 19 Bioactive Agent Incorporation/Release from a MD-AcrylateMatrix

500 mg of MD-Acrylate as prepared in Example 13 was placed in an 8 mLamber vial. To the MD-Acrylate was added 3 mg of MTA-PAAm (lyophilized),2 μL of 2-NVP, and 1 mL of 1× phosphate-buffered saline (1×PBS). Thereagents were then mixed for one hour on a shaker at 37° C. To thismixture was added either 5 mg 70 kD FITC-Dextran or 5 mg 100 kDFITC-Dextran (Sigma) and vortexed for 30 seconds. The mixture in anamount of 200 μL was placed into a Teflon well plate (8 mm diameter, 4mm deep) and illuminated for 40 seconds with an EFOS 100 SS illuminationsystem equipped with a 400-500 nm filter. The formed matrix was loose,and not as well crosslinked as the formed MD-acrylate matrix in Example17. After illumination, the matrix was transferred to a 12 well plate(Falcon) and placed in a well containing 0.6 mL PBS. At daily intervalsfor 6 days, 150 μL of PBS was removed from each well and placed into a96 well plate. The remaining 850 μL were removed from the samples, andreplaced with 1 mL fresh PBS. The 96 well plate was analyzed forFITC-Dextran on a spectrophotometer (Shimadzu) at 490 absorbance.Results showed that at least 70% of the detectable 10 kd or 70 kDFITC-Dextran was released from the matrix after 2 days. Visualobservation showed that an unquantified amount of 10 kD or 70 kDFITC-Dextran remained within the matrix after 6 days.

EXAMPLE 20 Enzyme Degradation of a MD-Acrylate Matrix

A MD-Acrylate-coated PEBAX rod (from Example 18) was placed in 5 mL of1× phosphate-buffered saline (PBS) containing 24 μg alpha-Amylase(Sigma; catalog # A6814) for 7 days on a rotating plate at 37° C. After7 days, the rod was removed from the PBS and washed with distilledwater. The rod was then examined under a Scanning Electron Microscope(LEO Supra 35 VP); upon examination, no trace of the MD-Acrylate coatingwas detected. As a control, a MD-Acrylate-coated PEBAX was placed in 1×phosphate-buffered saline (PBS) without alpha-Amylase; upon examination,the MD-Acrylate coating was intact and showed no signs of degradation.

EXAMPLE 21 Polyalditol-Acrylate Synthesis

Polyalditol (PA; GPC; 9.64 g; ˜3.21 mmole) was dissolved indimethylsulfoxide (DMSO) 60 mL. The size of the polyalditol wascalculated to be in the range of 2,000 Da-4,000 Da. A solution of EA-NCOfrom Example 12 (24.73 g; 19.3 mmole) was evaporated and dissolved indried DMSO (7.5 mL). The two DMSO solutions were mixed and heated to 55°C. overnight. The DMSO solution was placed in dialysis tubing (1000MWCO, 45 mm flat width×50 cm long) and dialyzed against water for 3days. The polyalditol macromer solution was filtered and lyophilized togive 7.91 g white solid. A sample of the macromer (49 mg), and DBB (4.84mg) was dissolved in 0.8 mL DMSO-d₆: ¹H NMR (DMSO-d₆, 400 MHz) δ 7.38(s, 4H; internal std. integral value of 2.7815), 6.50, 6.19, and 5.93(doublets, 3H; vinyl protons integral value of 3.0696). The calculatedacrylate load of macromer was 0.616 μmoles/mg of polymer.

EXAMPLE 22 Maltodextrin-Acrylate Filaments

1,100 milligrams of MD-Acrylate as prepared in Example 13 was placed inan 8 mL amber vial. To the MD-Acrylate was added 1 mg of aphotoinitiator 4,5-bis(4-benzoylphenyl-methyleneoxy)benzene-1,3-disulfonic acid (5 mg) (DBDS) and 1 mL of 1×phosphate-buffered saline (PBS). The reagents were then mixed for onehour on a shaker at 37° C. The mixture in an amount of 10 uL wasinjected, using a 23 gauge needle, into a 22 mm length opaque siliconetube (P/N 10-447-01; Helix Medical, Carpinteria, Calif.). The tubing wasplaced into a Dymax Lightweld PC-2 illumination system (Dymax Corp.;light intensity 6.5 mW/cm²), 15 cm from light source, illuminated for270 seconds, and then removed. After illumination, the filament wasremoved from the silicone tubing by rolling a pencil over the tubing,starting from the back. The filament was firm, which indicated completepolymerization of the MD-Acrylate. No excess liquid was observed. Thefilament was manipulated with forceps. Maltodextrin filaments were alsomade from a MD-acrylate solution having concentration of 200 mg/mL.These are physically firm and same as 1,100 mg/ml.

EXAMPLE 23 Polyalditol-Acrylate Filaments

1,500 milligrams of polyalditol-acrylate as prepared in Example 21 wasplaced in an 8 ml amber vial. To the polyalditol-acrylate was added 1 mgof DBDS (lyophilized), 15 mg Bovine Serum Albumin, and 200 uL of 1×phosphate-buffered saline (PBS). The reagents were then mixed for onehour on a shaker at 37° C. The mixture in an amount of 10 uL wasinjected, using a 23 gauge needle, into a 22 mm length opaque siliconetube (P/N 10-447-01; Helix Medical, Carpinteria, Calif.). The tubing wasplaced into a Dymax Lightweld PC-2 illumination system (Dymax Corp.;light intensity 6.5 mW/cm²), 15 cm from light source, illuminated for270 seconds, and then removed. After illumination, the filament wasremoved from the silicone tubing by rolling a pencil over the tubing,starting from the back. The filament was firm, which indicated completepolymerization of the polyalditol-acrylate. No excess liquid wasobserved. The filament was manipulated with forceps

EXAMPLE 24 Amylase Degradation of Maltodextrin-Acrylate Filaments

Maltodextrin-acrylate filaments were synthesized using 200 mg/mL and1100 mg/mL MD-acrylate as described in example 22 and were tested fordegradation in Amylase solutions. These filaments were placed inmicrocentrifuge tubes containing 1 mL of either 1×PBS (control), 1×PBScontaining alpha-Amylase at 0.121 μg/mL (Sigma; catalog # A6814), or1×PBS containing alpha-Amylase at 24 μg/mL. The tubes were then placedin an incubator at 37° C.

After 2 days in the PBS with the 0.121 μg/mL alpha-Amylase solution the200 mg/mL filament was completely degraded, and no trace of the filamentwas observable. The 200 mg/mL filament in PBS (control) showed no signsof degradation.

After 33 days in the 1×PBS containing alpha-Amylase at 0.121 μg/mL, the1100 mg/mL filament had lost some of its initial firmness (as noted bythe slightly curled appearance of the filament), but was stillcompletely intact. The 1,100 mg/mL filament in the PBS with 24 ugAmylase had completely degraded after 48 hours. The 1,100 mg/ml filamentin the PBS showed no signs of degradation.

EXAMPLE 25 Maltodextrin-Acrylate Filaments with Bioactive Agent andRelease

MD-Acrylate in an amount of 1,100 milligrams of as prepared in Example13 was placed in an 8 ml amber vial. To the MD-Acrylate was added 1 mgof DBDS (lyophilized), 15 mg Bovine Serum Albumin (representing thebioactive agent; and 1 mL of 1× phosphate-buffered saline (1×PBS). Thereagents were then mixed for one hour on a shaker at 37° C. The mixturein an amount of 10 uL was injected, using a 23 gauge needle, into a 22mm length opaque silicone tube (P/N 10-447-01; Helix Medical,Carpinteria, Calif.). The tubing was placed into a Dymax Lightweld PC-2illumination system (Dymax Corp.; light intensity 6.5 mW/cm²), 15 cmfrom light source, illuminated for 270 seconds, and then removed. Afterillumination, the filament was removed from the silicone tubing byrolling a pencil over the tubing, starting from the back. The filamentwas firm, which indicated complete polymerization of the MD-Acrylate. Noexcess liquid was observed.

The filament was placed in a 1.7 ml microcentrifuge tube with 1 ml1×PBS. At daily intervals for 6 days, 150 μL of PBS was removed fromeach well and placed into a 96 well plate for subsequent analysis. Theremaining 850 μL was removed from the sample, and to the tube was added1 ml of 1×PBS. After 6 days, the filament was placed in a 1.7 mlmicrocentrifuge tube with 1×PBS containing alpha-Amylase at 0.121 μg/mL.At daily intervals for 35 days, 150 μL of PBS was removed from each welland placed into a 96 well plate for subsequent analysis. The remaining850 μL was removed from the sample, and to the tube was added 1 ml offresh 1×PBS containing alpha-Amylase at 0.121 μg/mL. The 96-well platewas analyzed for BSA using the Quanitpro Assay Kit (Sigma). For thefirst 6 days, there was an initial burst of BSA, followed by a very slowrelease. After the addition of PBS+Amylase, the rate of BSA releasesignificantly increased, and was relatively constant over the next 35days. Results are shown in Table 2 and FIG. 1. TABLE 2 Cumulative BSArelease Timepoint (% of Total BSA) 1 4.8 2 5.35 3 5.7 4 5.98 5 6.19 66.36 7 9.46 8 10.7 9 11.82 10 12.94 11 14.01 12 15.06 13 16.11 14 17.2315 18.11 16 19.04 17 19.92 18 21.26 19 22.15 20 23.04 21 24.06 22 25.3523 26.31 24 26.91 25 27.51 26 28.63 27 29.19 28 29.75 29 30.44 30 31.1131 31.43 32 31.63 33 31.83 34 32.07 35 32.31 36 32.72 37 32.95 38 33.2739 33.83 40 34.15 41 34.43 42 34.71

EXAMPLE 26 Polyalditol-Acrylate Filaments with Bioactive Agent andRelease

Polyalditol-acrylate in an amount of 1,500 mg of as prepared in Example21 was placed in an 8 ml amber vial. To the PA-Acrylate was added 1 mgof DBDS (lyophilized), 15 mg Bovine Serum Albumin, and 1 mL of 1×phosphate-buffered saline (1×PBS). The reagents were then mixed for onehour on a shaker at 37° C. The mixture in an amount of 10 uL wasinjected, using a 23 gauge needle, into a 22 mm length opaque siliconetube (P/N 10-447-01; Helix Medical, Carpinteria, Calif.). The tubing wasplaced into a Dymax Lightweld PC-2 illumination system (Dymax Corp.;light intensity 6.5 mW/cm²), 15 cm from light source, illuminated for270 seconds, and then removed. After illumination, the filament wasremoved from the silicone tubing by rolling a pencil over the tubing,starting from the back. The filament was firm, which indicated completepolymerization of the polyalditol-acrylate. No excess liquid wasobserved. The filament was manipulated with forceps.

The filament was placed in a 1.7 ml microcentrifuge tube with 1 ml PBScontaining alpha-Amylase at 0.121 μg/mL. At daily intervals for 15 days,150 μl of PBS was removed from each well and placed into a 96 well platefor subsequent analysis. The remaining 850 μL was removed from thesample, and to the tube was added 1 ml of fresh PBS containingalpha-Amylase at 0.121 μg/mL. The 96-well plate was analyzed for BSAusing the Quanitpro Assay Kit (Sigma).

EXAMPLE 27 Maltodextrin-Acrylate Filaments with Bioactive Agent andRelease

Maltodextrin filaments were synthesized using a 1,100 mg/mL solution asdescribed in example 25 using an anti-horseradish peroxidase antibody(P7899; Sigma) instead of BSA. The filament contained 800 ug of theanti-horseradish peroxidase antibody. The filament was placed in a 1.7ml microcentrifuge tube containing 1 ml of 1×PBS containingalpha-Amylase at 0.121 μg/mL. At daily intervals for 5 days, 100 μl ofPBS was removed from the sample, placed into a 96 well plate andincubated for 60 minutes at 37° C. The remaining 850 μL was removed fromthe sample, and replaced with 1 ml fresh 1×PBS containing alpha-Amylaseat 0.121 μg/mL. After 1 hour, the plate was washed three times with 1 mlPBS/Tween (Sigma). 150 ul StabilCoat™ Immunoassay Stabilizer (SurModics,Eden Prairie, Minn.) was added to the well and incubated for 30 minutesat room temperature. After 30 minutes, the 96-well plate was washedthree times with PBS/Tween. A solution of 0.5 mg/ml HorseradishPeroxidase (Sigma) in 1×PBS (100 uL) was added to the well and incubatedfor 60 minutes. After 60 minutes, the 96-well plate was washed six timeswith PBS/Tween. A chromogenic assay was then performed. After 15minutes, the 96 well plate was analyzed for HRP conjugate on aspectrophotometer (Tecan) at 560 nm absorbance. Detectable Antibody wasfound at each time point.

EXAMPLE 28 Bioactive Agent Incorporation and Release from aMD-Acrylate/Photo-PVP-Coated PEBAX Rod

100 mg photo-PVP and 5 mg the photoinitiator tetra-BBE-PET were mixedwith 10 ml Isopropyl alcohol (IPA; Fisher) for 1 minute. The mixture inan amount of 1 ml was placed into a 1.7 ml eppendorf tube (VWR). A 1.2cm PEBAX® rod (Medical Profiles, Inc) was dipped into the solution for10 seconds, at a dip rate of 0.75 cm/second, and then removed at thesame rate. The rod was allowed to air dry for 10 minutes. The rod wasplaced into a Dymax Lightweld PC-2 illumination system (Dymax Corp.;light intensity 6.5 mW/cm²), 30 cm from light source, illuminated for180 seconds, and then removed.

1000 mg of MD-Acrylate, as prepared in Example 13 was placed in an 8 mLamber vial. To the MD-Acrylate was added 5 mg DBDS, 1 ml of 1×phosphate-buffered saline (PBS), and 100 mg BSA. The reagents were thenmixed for one hour on a shaker at 37° C. The mixture in an amount of 1ml was placed into a 1.8 ml eppendorf tube (VWR). Thephoto-PVP/tetra-BBE-PET coated PEBAX® rod was dipped into the mixturefor 30 seconds, at a dip rate of 0.3 cm/s, and then removed at the samerate. The rod was immediately placed into a Dymax Lightweld PC-2illumination system (Dymax Corp.; light intensity 6.5 mW/cm²), 30 cmfrom light source, and illuminated for 180 seconds and then removed.

The rod was placed in a 1.7 ml microcentrifuge tube with 1 ml 1×PBScontaining alpha-Amylase at 0.121 μg/mL. At intervals for 9 days, 150 μlof PBS was removed from each well and placed into a 96 well plate. Theremaining 850 μl were removed from the samples, and replaced with 1 mlfresh 1×PBS containing alpha-Amylase at 0.121 μg/mL. The 96 well-platewas analyzed for BSA release using the Quanitpro Assay Kit (Sigma). BSAwas detected at each timepoint. Results are shown in Table 3 and FIG. 2.TABLE 3 Timepoint Cumulative BSA release (% of Total BSA) 1 7.0 2 15.0 319.1 4 22.7 5 25.6 7 28.6 8 31.5 9 34.2

EXAMPLE 29 Degradation of MD-Acrylate Coating

The MD-Acrylate-coated PEBAX rod (as prepared in Example 28) was placedin 5 ml of 1× phosphate-buffered saline (PBS) containing alpha-Amylaseat 24 μg/mL for 7 days on a rotating plate at 37° C. After 7 days, therod was removed from the PBS and washed with distilled water. The rodwas then examined under a Scanning Electron Microscope (LEO Supra 35VP); upon examination, no trace of the MD-Acrylate coating was detected.

EXAMPLE 30 Degradation of MD-Acrylate Filament in Vitreal Fluid

A circumferential dissection of the anterior segment (cornea, aqueoushumour, lens) of porcine eye was performed, and the vitreous wassqueezed out from the globe into a 20 mL amber vial; approx 10 mL totalwas retrieved from a total of four eyes. 200 mg/mL and 1100 mg/mLMaltodextrin filaments, formed in example 21, were placed into 2 mL ofthe vitreous solution, and placed at 37° C. on a rotator plate. The 200mg/mL filament had completely dissolved after 24 hours. The 1,100 mg/mLfilaments completely degraded after 30 days in the vitreous.

EXAMPLE 31 Formation of a Maltodextrin-Acrylate Biodegradable MatrixUsing REDOX Chemistry

Two solutions were prepared. Solution #1 was prepared as follows: 250 mgof MD-acrylate as prepared in example 13 was placed in an 8 mL vial. Tothe MD-acrylate was added 15 mg ferrous gluconate hydrate (Sigma), 30 mgAscorbic Acid (Sigma), 67 uL AMPS (Lubrizol) and 1,000 uL deionizedwater. Solution #2 was prepared as follows: 250 mg of MD-acrylate asprepared in example 13 was placed in a second 8 mL vial. To thisMD-acrylate was added 30 uL AMPS, 80 uL Hydrogen Peroxide (Sigma) and890 uL 0.1 M Acetate buffer (pH 5.5).

50 uL of Solution #1 was added to a glass slide. 50 uL of solution #2was added to Solution #1 with slight vortexing. After mixing for 2seconds, the mixture polymerized and formed a semi-firm gel havingelastomeric properties.

EXAMPLE 32 Formation of Maltodextrin-Acrylate Biodegradable Matrix UsingREDOX Chemistry

Two solutions were prepared, similar to Example 31, but in this ExampleSolution #1 different concentrations of ferrous gluconate hydrate(Sigma) and ascorbic acid were used. Solution #1 was prepared asfollows: 250 mg of MD-acrylate (as prepared in example 13) was placed inan 8 mL vial. To the MD-acrylate was added 5 mg ferrous gluconatehydrate (Sigma), 40 mg ascorbic acid (Sigma), 67 uL AMPS (Lubrizol) and1,000 uL deionized water. Solution #2 was prepared as follows: 250 mg ofMD-acrylate as prepared in example 7 was placed in a second 8 mL vial.To this MD-acrylate was added 30 uL AMPS, 80 uL Hydrogen Peroxide(Sigma) and 890 uL 0.1 M Acetate buffer (pH 5.5).

50 uL of Solution #1 was added to a glass slide. 50 uL of solution #2was added to Solution #1 with slight vortexing. After mixing for 8seconds, the mixture polymerized and formed a semi-firm gel havingelastomeric properties.

EXAMPLE 33 Formation of Maltodextrin-acrylate Biodegradable Matrix UsingREDOX Chemistry

Two solutions were prepared. Solution #1 was prepared as follows: 250 mgof MD-acrylate (as prepared in example 13) was placed in an 8 mL vial.To the MD-acrylate was added 15 mg Iron (II) L-Ascorbate (Sigma), 30 mgAscorbic Acid (Sigma), 67 uL AMPS (Lubrizol) and 1,000 uL deionizedwater. Solution #2 was prepared as follows: 250 mg of MD-acrylate asprepared in example 7 was placed in a second 8 mL vial. To thisMD-acrylate was added 30 uL AMPS, 80 uL hydrogen peroxide (Sigma) and890 uL 0.1 M Acetate buffer (pH 5.5).

50 uL of Solution #1 was added to a glass slide. 50 uL of solution #2was added to Solution #1 with slight vortexing. After mixing for 2seconds, the mixture polymerized and formed a semi-firm gel havingelastomeric properties.

EXAMPLE 34 Formation of Polyalditol-Acrylate Biodegradable Matrix UsingREDOX Chemistry

Two solutions were prepared. Solution #1 was prepared as follows: 1,000mg of Polyalditol-acrylate as prepared in Example 21 was placed in an 8mL vial. To the Polyalditol-acrylate was added 15 mg Ferrous SulfateHeptahydrate (Sigma), 30 mg Ascorbic Acid (Sigma), 67 uL AMPS (Lubrizol)and 1,000 uL deionized water; Solution #2 was prepared as follows: 1,000mg of Polyalditol-acrylate as prepared in example was placed in a second8 mL vial. To this Polyalditol-acrylate was added 30 uL AMPS, 80 uLHydrogen Peroxide (Sigma) and 890 uL 0.1 M Acetate buffer (pH 5.5).

50 uL of Solution #1 was added to a glass slide. 50 uL of solution #2was added to Solution #1 with slight vortexing. After mixing for 2seconds, the mixture polymerized and formed a semi-firm gel havingelastomeric properties.

EXAMPLE 35 Coating a PEBAX® Rod with MD-Acrylate Using REDOX

Photo-PVP (100 mg) and the photoinitiator tetra-BBE-PET (5 mg), weremixed with 10 mL isopropyl alcohol (IPA; Fisher) for 1 minute. Themixture in an amount of 1 mL was placed into a 1.8 mL eppendorf tube(VWR). A 1.2 cm PEBAX® rod (Medical Profiles, Inc) was dipped into thesolution for 10 seconds, at a dip rate of 0.1 cm/second, and thenremoved at the same rate. The rod was allowed to air dry for 5 minutes.The rod was placed into a Dymax Lightweld PC-2 illumination system(Dymax Corp.; light intensity 6.5 mW/cm²), 30 cm from light source,illuminated for 180 seconds, and then removed.

Two solutions were prepared. Solution #1 was prepared as follows: 250 mgof MD-acrylate (as prepared in example 13) was placed in an 8 ml vial.To the MD-acrylate was added 15 mg Iron (II) Ascorbate (Sigma), 30 mgAscorbic Acid (Sigma), 67 ul AMPS (Lubrizol) and 1,000 ul deionizedwater. Solution #2 was prepared as follows: 250 mg of MD-acrylate wasplaced in a second 8 ml vial. To this MD-acrylate was added 30 ul AMPS,80 ul Hydrogen Peroxide (Sigma) and 890 ul 0.1 M Acetate buffer (pH5.5).

Solution #1 in an amount of 1 mL was placed into a 1.8 mL eppendorf tube(VWR). The photo-PVP/tetra-BBE-PET coated PEBAX® rod was dipped into themixture for 30 seconds, at a dip rate of 0.5 cm/s, and then removed atthe same rate. The PEBAX rod was allowed to air dry for 10 minutes.Solution #2 in an amount of 1 mL was placed into a second 1.8 mLeppendorf tube (VWR). The photo-PVP/tetra-BBE-PET and Solution #1 coatedPEBAX® rod was dipped into the mixture for 30 seconds, at a dip rate of0.5 cm/s, and then removed at the same rate.

The MD-Acrylate coated rod was examined under Scanning ElectronMicroscope (SEM; LEO Supra 35 VP); the MD-Acrylate coating thicknessranged from 15 to 20 um, with an average thickness of 16.8 um.

EXAMPLE 36 Bioactive Agent Incorporation into a MD-Acrylate Matrix

Two solutions were prepared. Solution #1 was prepared as follows: 250 mgof MD-acrylate (as prepared in example 13) was placed in an 8 ml vial.To the MD-acrylate was added 15 mg Iron (II) Acetate (Sigma), 30 mgAscorbic Acid (Sigma), 67 ul AMPS (Lubrizol), 75 mg Bovine Serum Albumin(BSA; representing the bioactive agent) and 1,000 μL deionized water.Solution #1 was prepared as follows: 250 mg of MD-acrylate was placed ina second 8 ml vial. To this MD-acrylate was added 30 μL AMPS, 80 μLHydrogen Peroxide (Sigma), 75 mg BSA and 890 μL Acetate buffer (pH 5.5).

50 μL of Solution #1 was added to a glass slide. 50 μL of solution #2was added to Solution #1 with slight vortexing. After mixing for 2seconds, the mixture polymerized and formed a semi-firm gel havingelastomeric properties.

EXAMPLE 37 Enzyme Degradation of a MD-Acrylate Matrix Formed by REDOX

Maltodextrin-acrylate filaments were prepared using the reagents atconcentrations as described in Example 31. These filaments were placedin microcentrifuge tubes containing 1 ml either Phosphate BufferedSaline (PBS) or 1×PBS containing alpha-Amylase at 0.121 μg/mL. The tubeswere then placed in an incubator at 37° C.

After 4 days in the 1×PBS containing alpha-Amylase at 0.121 μg/mL, the250 mg/mL filament had completely degraded, leaving no trace of thematrix. The matrix in PBS showed no signs of degradation.

EXAMPLE 38 FAB Fragment Incorporation and Release from a MD-AcrylateFilament

600 milligrams of MD-Acrylate as prepared in Example 13 was placed in an8 mL amber vial. To the MD-Acrylate was added 5 mg of DBDS(lyophilized), 10 mg Rabbit Anti-Goat Fragment Antibody (catalog #300-007-003; Jackson Immunological Research, West Grove, Pa.) and 1 mLof 1× phosphate-buffered saline (PBS). The reagents were then mixed forone hour on a shaker at 37° C. The mixture in an amount of 10 μL waspipetted into a 22 mm length opaque silicone tube (P/N 10-447-01; HelixMedical, Carpinteria, Calif.). The tubing was placed into a DymaxLightweld PC-2 illumination system (Dymax Corp.; light intensity 6.5mW/cm²), 15 cm from light source, illuminated for 270 seconds, and thenremoved. After illumination, the filament was removed from the siliconetubing by rolling a pencil over the tubing, starting from the back. Thefilament was firm and completely crosslinked, with no excess liquid. Thefilament was placed in a 1.7 mL microcentrifuge tube with 0.5 ml 1×PBScontaining alpha-Amylase at 0.121 μg/mL (eluent solution). Atpredetermined intervals for 17 days, 200 μL of the eluent solution wasremoved from each tube, and 100 μL was placed into two 96 well plates.The remaining 300 μL were removed from the samples, and replaced with0.5 mL fresh 1×PBS containing alpha-Amylase at 0.121 μg/mL. The 96 wellplates were analyzed for total FAB molecule release and FAB activityusing an Enzyme-Linked Immunosorbent Assay (ELISA). Briefly, the 100 μLeluent solution was incubated at 37° C. for one hour and then washed 3×with 2 ml PBS/Tween 20 (Sigma). The wells were blocked with 100 μLStabilCoat™ for 1 hour at room temperature and then washed 3× with 2 mLPBS/Tween 20. 100 uL of either 0.1 ug/mL (in PBS/Tween) HRP-labeled GoatIgG (Jackson Immunological; catalog #005-030-003) for molecule activityor 0.08 ug/mL (in PBS/Tween) HRP-labeled Goat anti-Rabbit IgG (JacksonImmunological; catalog #111-305-003) was incubated for 1 hour at 37° C.The wells were washed 6× with 2 mL PBS/Tween 20. 100 μL of TMB MicrowellPeroxidase Substrate System (KPL, Catalog #50-76-00; Gaithersburg, Md.)as added to each well. After 15 minutes, the 96 well plate was analyzedfor HRP conjugate on a spectrophotometer (Tecan) at 650 nm absorbance.Detectable Antibody was found at each timepoint. Results are shown inTable 4 and FIG. 3. TABLE 4 Fab Fragment release ABS values CumulativeActive FAB Cumulative Total Fab Timepoint (Day) Abs at 650 nm Abs at 650nm 1 1.37 1.97 3 3.12 4.07 4 4.54 5.87 6 5.69 7.54 7 6.12 8.60 8 6.539.01 10 6.94 9.79 13 7.34 10.64 15 7.54 11.18 17 7.71 11.62 19 7.8111.92 21 7.90 12.28 23 8.00 12.68 26 8.09 13.11

EXAMPLE 39 Rabbit Antibody Incorporation and Release from a MD-Acrylate(Redox Polymerization) Coated Stainless Steel Rod

316V or 304V stainless steel rods (0.035″ diameter; Small Parts, Inc.)were cleaned by wiping the rods with isopropyl alcohol (IPA) soakedAlpha 10 clean-wipes (Texwipe; Kernersville, N.C.) and then sonicatingthe rods in a solution of 10% Valtron SP2200 detergent (Valtech Corp.)in hot tap water for 10 minutes. The rods were then rinsed 3× withdeionized water followed by a 1 minute sonication in hot tap water; therinse and sonication steps were then repeated.

A 0.5% 1,4-bis(trimethoxysilylethyl)benzene (B2495.6, UCT, Bristol, Pa.)solution in 89.5% IPA and 10% deionized water was prepared (See Example1 of U.S. Pat. No. 6,706,408B2-) and the cleaned rods were dipped intothe silane solution within 2 minutes of coming out of the deionizedrinse. The rods were allowed to dwell in the silane solution for 3minutes and then pulled out at a rate of 1.0 cm/s. They were allowed toair dry for 2 minutes at room temperature and then placed at 110° C. for5 minutes.

A solution of photo-PVP (15 mg/mL), DBDS (1 mg/mL), tetra-BBE-PET 0.075(mg/mL) and PVP K90 (20 mg/ml; BASF) was prepared in 60% IPA/40% water)(see also Example 1 of U.S. Pat. No. 6,706,408B2). The silane treatedrods were dip coated into the above solution using the followingparameters:

Velocity in=2.0 cm/s; dwell time=60 seconds; velocity out=0.1 cm/s Thecoated rods were allowed to air dry at room temperature for 5 minutesand then illuminated in a Dymax lamp UV light chamber, with rotation,for 3 minutes. The dipping procedure was then repeated with a dwell timeof 120 seconds (all other dipping parameters the same).

Two solutions were prepared. The first solution (#1) was prepared byplacing 600 mg of MD-acrylate (as prepared in example 13) into an 8 mLvial and then adding 9 mg iron (II) ascorbate (Sigma), 30 mg ascorbicacid (Sigma), 67 μL AMPS (Lubrizol), 16 mg Rabbit Anti-HRP antibody(Sigma; catalog # P7899), and 1,000 μL deionized water. The secondsolution (#2) was prepared by placing 600 mg of MD-acrylate in a second8 mL vial and then adding 30 μL AMPS, 16 mg Rabbit Anti-HRP antibody(Sigma; catalog # P7899), 80 μL hydrogen peroxide (Sigma) and 890 μL 0.1M Acetate buffer (pH 5.5).

Solution #1 in an amount of 1 mL was placed into a 1.8 mL eppendorf tube(VWR). The (PV01/K90/DBDS/tetra-BBE-PET)-coated stainless steel rod (20mm in length) was dipped into the mixture for 20 seconds, at a dip rateof 0.75 cm/s, and then removed at the same rate. The rod was allowed toair dry for 10 minutes. Solution #2 in an amount of 1 mL was placed intoa second 1.8 mL eppendorf tube (VWR). The(PV01/K90/DBDS/tetra-BBE-PET)-coated and Solution #1 coated rod wasdipped into the Solution #2 for 20 seconds, at a dip rate of 0.75 cm/s,and then removed at the same rate. Contact with Solution #2 initiatedthe redox reaction and caused formation of an MD-Acrylate coated layeron the PV01/K90/DBDS/tetra-BBE-PET coated layer; the MD-Acrylate coatingwas cured within 10 seconds

The coated rod was examined under Optical Inferometer Microscope (Veeco)which revealed that the MD-Acrylate coating layer had a thickness of 70μm.

The MD-Acrylate coated rod was placed in a 0.6 mL microcentrifuge tubewith 0.5 ml 1×PBS containing alpha-Amylase at 0.121 μg/mL (eluentsolution) to assess release of the bioactive agent (antibody) from thecoating.

At predetermined intervals for 19 days, 200 μL of the eluent solutionwas removed from the tube, which was divided into two 100 μL aliquotsand placed into two 96 well plates. The remaining 300 μL was removedfrom the microcentrifuge tube, and 0.5 mL of fresh eluent solution(1×PBS containing alpha-Amylase at 0.121 μg/mL) was added to themicrocentrifuge tube having the MD-Acrylate coated rod. The eluentsamples in 96 well plates were analyzed for total Rabbit Antibodymolecule release and activity using an Enzyme-Linked Immunosorbent Assay(ELISA). Briefly, the 100 μL of eluent solution was incubated at 37° C.for one hour and then washed 3× with 2 ml PBS/Tween 20 (Sigma). Thewells were blocked with 100 μL StabilCoat™ (SurModics, Eden Prairie,Minn.) for 1 hour at room temperature and then washed 3× with 2 mlPBS/Tween 20. 100 μL of either 0.1 ug/mL (in PBS/Tween) HRP (Sigma;catalog # P8375) for molecule activity or 0.08 ug/mL (in PBS/Tween)HRP-labeled Goat anti-Rabbit IgG (Jackson Immunological; catalog #111-305-003) was incubated for 1 hour at 37° C. The wells were washed 6×with 2 ml PBS/Tween 20. 100 μL of TMB Microwell Peroxidase SubstrateSystem (KPL, Catalog # 50-76-00; Gaithersburg, Md.) was added to eachwell. After 15 minutes, the 96 well plate was analyzed for HRP conjugateon a spectrophotometer (Tecan) at 650 nm absorbance. Detectable antibodywas found in the eluate samples at each timepoint. Results are shown inTable 5 and FIG. 4. TABLE 5 Cumulative Active IgG Cumulative Total IgGTimepoint (Day) Abs at 650 nm Abs at 650 nm 1 1.08 2.01 2 1.82 3.78 42.01 5.11 6 2.41 5.57 8 2.48 5.75 10 2.54 5.88 12 2.59 5.97 19 2.87 7.88

EXAMPLE 40 Rabbit Antibody Incorporation and Release from a MD-Acrylate(Photo-Initiated Polymerization) Coated Stainless Steel Rod

316V or 304V stainless steel rods (0.035″ diameter; Small Parts, Inc.,Miami Lakes, Fla.) were cleaned by wiping the rods with isopropylalcohol (IPA)-soaked Alpha 10 clean-wipe (Texwipe) and then sonicatingthe rods in a solution of 10% Valtron SP2200 detergent in hot tap waterfor 10 minutes. The rods were then rinsed 3× with deionized waterfollowed by a 1 minute sonication in hot tap water; the rinse andsonication step was then repeated.

The cleaned rods were dipped into a 0.5% 1,4-bis(trimethoxysilylethyl)benzene solution (as described in Example 39) within 2 minutes of comingout of the deionized rinse. The rods were allowed to dwell in the silanesolution for 3 minutes and then pulled out at a rate of 1.0 cm/s. Therods were allowed to air dry for 2 minutes at room temperature and thenplaced at 110° C. for 5 minutes.

A solution of PV01 (15 mg/mL), DBDS (1 mg/mL), tetra-BBE-PET (0.075mg/ml) and K90 (20 mg/mL; BASF) was prepared in 60% IPA/40% water. Thesilane treated rods were dip coated into the above solution using thefollowing parameters:

Velocity in =2.0 cm/s; dwell time=60 seconds; velocity out=0.1 cm/s. Thecoated rods were allowed to air dry at room temperature for 5 minutesand then illuminated in a Dymax lamp UV light chamber, with rotation,for 3 minutes. The dipping procedure was then repeated with a dwell timeof 120 seconds (all other dipping parameters the same).

600 milligrams of MD-Acrylate as prepared in Example 13 was placed in an8 mL amber vial. To the MD-Acrylate was added 5 mg of DBDS(lyophilized), 16 mg Rabbit Anti-HRP antibody (Sigma; catalog # P7899)and 1 ml of 1× phosphate-buffered saline (PBS). The reagents were thenmixed for one hour on a shaker at 37° C. The MD-Acrylate solution in anamount of 1 mL was placed into a 1.8 mL eppendorf tube (VWR). The(PV01/K90/DBDS/tetra-BBE-PET)-coated stainless steel rod (20 mm inlength) was dipped into the mixture for 20 seconds, at a dip rate of0.75 cm/s, and then removed at the same rate. The rod was thenimmediately illuminated in a Dymax lamp UV light chamber, with rotation,for 3 minutes. The rod was allowed to air dry for 5 minutes, and thedipping and illuminating procedures were repeated one more time.

The MD-Acrylate coated rod was examined under Optical InferometerMicroscope (Veeco); the MD-Acrylate coating layer had a coatingthickness of 20 μm.

The MD-Acrylate coated rod was placed in a 0.6 mL microcentrifuge tubewith 0.5 mL 1×PBS containing alpha-Amylase at 0.121 μg/mL (eluentsolution) to assess degradation of the coating and release of thebioactive agent (antibody) from the coating. At predetermined intervalsfor 25 days, 200 μL of the eluent solution was removed from each tube,which was divided into two 100 μL aliquots and placed into two 96 wellplates. The remaining 300 μL was removed from the microcentrifuge tube,and 0.5 mL of fresh eluent solution (1×PBS containing alpha-Amylase at0.121 μg/mL) was added to the microcentrifuge tube having theMD-Acrylate coated rod.

The 96 well plates were analyzed for total Rabbit Antibody moleculerelease and activity using an Enzyme-Linked Immunosorbent Assay (ELISA).Briefly, the 100 μL eluent solution was added to the wells and incubatedat 37° C. for one hour and then washed 3× with 2 mL PBS/Tween 20(Sigma). The wells were blocked with 100 μL StabilCoat™ for 1 hour atroom temperature and then washed 3× with 2 mL PBS/Tween 20. 100 μL ofeither 0.1 ug/mL (in PBS/Tween) HRP (Sigma; catalog # P8375) formolecule activity or 0.08 ug/mL (in PBS/Tween) HRP-labeled Goatanti-Rabbit IgG (Jackson Immunological; catalog # 111-305-003) wasincubated for 1 hour at 37° C. The wells were washed 6× with 2 mLPBS/Tween 20. 100 μL of TMB Microwell Peroxidase Substrate System (KPL,Catalog # 50-76-00; Gaithersburg, Md.) was added to each well. After 15minutes, the 96 well plate was analyzed for HRP conjugate on aspectrophotometer (Tecan) at 650 nm absorbance. Detectable antibody wasfound in the eluate samples at each time point.

Based on the initial weight of the coating before degradation, atheoretical maximum concentration of the antibody was calculated. Inaddition to measurements performed by ELISA, the MD-Acrylate coated rodwas weighed at various time points to determine the amount of materialof the MD-Acrylate coated layer lost from the rods due to amylasedigestion. Results are shown in Table 6 and FIG. 5. TABLE 6 MaximumCumulative Cumulative MD-acrylate theoretical Active Total coating totalTimepoint IgG release (%) IgG release (%) remaining IgG release (Day)(ELISA) (ELISA) (%) (%) 1 7.14 9.29 2 8.14 10.14 83 17 4 8.49 10.29 68.93 10.49 7 80 20 8 9.27 10.76 10 9.63 10.90 12 10.06 11.19 14 10.1911.36 80 20 17 10.65 11.91 19 11.19 12.68 22 12.62 13.38 25 14.76 14.35

EXAMPLE 41 Rabbit Antibody Incorporation and Release from a MD-AcrylateFilament

600 milligrams of MD-Acrylate as prepared in Example 13 was placed in an8 ml amber vial. To the MD-Acrylate was added 5 mg of DBDS(lyophilized), 16 mg Rabbit Antibody Anti-HRP (Sigma; catalog # P7899)and 1 ml of 1× phosphate-buffered saline (PBS). The reagents were thenmixed for one hour on a shaker at 37° C. The mixture in an amount of 10μL was pipetted into a 22 mm length opaque silicone tube (P/N 10-447-01;Helix Medical, Carpinteria, Calif.). The tubing was placed into a DymaxLightweld PC-2 illumination system (Dymax Corp.; light intensity 6.5mW/cm²), 15 cm from light source, illuminated for 270 seconds, and thenremoved. After illumination, the filament was removed from the siliconetubing by rolling a pencil over the tubing, starting from the back. Thefilament was firm and completely crosslinked, with no excess liquid.

The filament was placed in a 1.7 ml microcentrifuge tube with 0.5 ml1×PBS containing alpha-Amylase at 0.121 μg/mL (eluent solution). Atpredetermined intervals for 25 days, 200 μl of the eluent solution wasremoved from each tube, and 100 μL was placed into two 96 well plates.The remaining 300 μl were removed from the samples, and replaced with0.5 ml fresh 1×PBS containing alpha-Amylase at 0.121 μg/mL. The 96wellplates were analyzed for total Rabbit Antibody molecule release andactivity using an Enzyme-Linked Immunosorbent Assay (ELISA). Briefly,the 100 μL eluent solution was added to the wells and incubated at 37degrees C. for one hour and then washed 3× with 2 ml PBS/Tween 20(Sigma). The wells were blocked with 100 μL StabilCoat™ (SurModics) for1 hour at room temperature and then washed 3× with 2 ml PBS/Tween 20.100 μL of either 0.1 ug/ml (in PBS/Tween) HRP (Sigma; catalog # P8375)for molecule activity or 0.08 ug/ml (in PBS/Tween) HRP-labeled Goatanti-Rabbit IgG (Jackson Immunological; catalog # 111-305-003) wasincubated for 1 hour at 37 degrees C. The wells were washed 6× with 2 mlPBS/Tween 20. 100 μL of TMB Microwell Peroxidase Substrate System (KPL,Catalog # 50-76-00; Gaithersburg, Md.) was added to each well. After 15minutes, the 96 well plate was analyzed for HRP conjugate on aspectrophotometer (Tecan) at 650 nm absorbance. Detectable Antibody wasfound at each time point.

Results are shown in Table 7 and FIG. 6. TABLE 7 Maximum CumulativeCumulative MD-acrylate theoretical Active Total coating total TimepointIgG release (%) IgG release (%) remaining IgG release (Day) (ELISA)(ELISA) (%) (%) 1 5.56 5.31 2 12.13 11.94 4 18.38 19.13 6 27.75 22.88 783 17 8 33.50 25.44 10 37.63 27.44 12 39.50 28.31 14 40.75 28.57 59 3117 41.75 28.76 19 42.75 28.98 21 40 60 22 43.44 29.67 25 44.31 30.67

EXAMPLE 42 Mechanical Testing of MD-Acrylate Discs Formed Via RedoxPolymerization

MD-acrylate discs formed via redox polymerization of MD-acrylate coatingsolutions were tested for mechanical properties.

A first solution (#1) was prepared by placing 300 mg of MD-acrylate asprepared in Example 13 into an 8 ml vial and then adding 9 mg iron (II)ascorbate (Sigma), 30 mg ascorbic acid (Sigma), 67 μL AMPS (Lubrizol),and 1,000 μL deionized water. Solution #2 was prepared by placing 300 mgof MD-acrylate into a second 8 ml vial and then added 30 μL AMPS, 80 μLif hydrogen peroxide (Sigma) and 890 μL of 0.1 M Acetate buffer (pH5.5).

Viscosity of the first and second solutions were determined on aBrookfield Viscometer. The average viscosity for both solutions was 10.9cP.

The modulus of the formed matrix was determined by rheologicalmeasurements. In order to perform rheological measurements, the firstand second solutions were combined on the testing plate in the Rheometer(Rheometric Scientific; model # SR-2000) and the mixture was allowed topolymerize to form a matrix. Data recording began before sample wascured in plates. Briefly, 100 μL of solution #1 and 100 μL of solution#2 were mixed on the lower testing plate. As the matrix formed, theupper testing plate was lowered to fully contact the mixture of thefirst and second solutions as the mixture polymerized into a matrix. Thesample was cured within 15 seconds. This curing method ensured maximumcontact between the two testing plates resulting in more accuratetesting compared to pre-formed matrices being placed between the testingplates. The resulting MD-acrylate matrix had properties of an elasticsolid with an elastic (storage) modulus ranging from 27 kPa to 30 kPa,and a viscous (loss) modulus of only about 1 kPa. Results are shown inTable 8 and FIG. 7. TABLE 8 (Testing Conditions: Stress: 433 Pa; strain1.6%; frequency: 1 radian/sec) G′ (Elastic G″ (Storage G* (Loss Time(seconds) Modulus; Pa) Modulus; Pa) Modulus; Pa) 247 26820.2 1300.526851.7 261 26908.5 1294.55 26939.6 274 26872 1299.28 26903.4 28826943.8 1343.69 26977.3 301 27376.6 1380.43 27411.4 315 27327.7 1373.3127362.2 329 27319.8 1376.27 27354.5 342 27274.8 1362.35 27308.8 35627246.6 1369.38 27281 369 27180.6 1373.6 27215.3 383 27174.4 1371.6127209 397 27119.4 1366.76 27153.9 410 27105.4 1360.49 27139.5 42427064.1 1358.45 27098.2 437 27019.9 1355.9 27053.9 451 27019.8 1355.3927053.8 465 26972.3 1355.85 27006.4 478 26956.2 1361.11 26990.5 49226918.2 1352.58 26952.2 505 26880.7 1355.85 26914.9 519 26840.4 1360.4726874.9

EXAMPLE 43 Lubricity and Durability Testing of MD-Acrylate Coated PEBAXRods

To assess lubricity and tenacity of MD-acrylate coated parts, frictionalforce testing was performed.

Frictional testing over the last 40 cycles of a 50 cycle test wasevaluated. Coated rods were evaluated a horizontal sled style frictiontest method (modified ASTM D-1894, as described below). Silicone Pads (7mm diameter) were hydrated and then wrapped around a 200 gram stainlesssteel sled. The silicone pad was clipped together tightly on theopposite side of the sled. The sled with rotatable arm was then attachedto a 500 gram Chatillon Digital Force Gauge (DGGHS, 500×0.1) withcomputer interface. The testing surface was mounted on a 22.5 inchpositioning rail table with micro-stepper motor control (Compumotor SX6Indexer/Drive).

MD-coated rods (from example 18) were hydrated in deionized water andclamped onto the test surface 1 inch (or approximately 2.5 cm) apart.The hydrated Silicone pad (jaw force set at 500 g) moved at 0.5 cm/secover a 5 cm section for 50 push/pull cycles, and the final forcemeasurements were taken over the last 40 push/pull cycles.

As shown in Table 9 and FIG. 8, compared to the benchmark syntheticcoating (see example 1 of U.S. Pat. No. 6,706,408B2) the MD-acrylatecoated rod provided a coating having excellent lubricity and durability;the rods coated with a MD-acrylate formulation containing aphotoinitiator, the grams of force remained relatively constant for thelast 40 cycles, indicating a durable coating. TABLE 9 MD-acrylate photocoated rod Synthetic 1 9.67 12.53 2 9.53 12.43 3 9.45 12.26 4 9.18 12.405 9.12 12.33 6 9.13 12.17 7 9.11 12.15 8 9.06 12.12 9 8.92 12.25 10 8.9612.19 11 8.91 12.11 12 8.98 12.02 13 8.95 12.02 14 8.82 12.25 15 8.7912.10 16 8.84 12.08 17 8.85 12.02 18 8.89 11.92 19 8.76 12.10 20 8.8112.08 21 8.85 11.93 22 8.85 11.86 23 8.88 11.83 24 8.81 12.01 25 8.9011.94 26 8.96 11.94 27 9.04 11.87 28 9.04 11.71 29 8.97 12.00 30 9.0311.94 31 9.05 11.79 32 9.20 11.83 33 9.32 11.75 34 9.23 11.90 35 9.2211.82 36 9.39 11.79 37 9.46 11.68 38 9.52 11.74 39 9.53 11.91 40 9.5611.87

EXAMPLE 44 Preparation of Acylated Maltodextrin (Butyrylated-MD)

Maltodextrin having pendent butyryl groups were prepared by couplingbutyric anhydride at varying molar ratios.

To provide butyrylated-MD (1 butyl/4 glucose units, 1:4 B/GU) thefollowing procedure was performed. Maltodextrin (MD; Aldrich; 11.0 g;3.67 mmole; DE (Dextrose Equivalent): 4.0-7.0) was dissolved indimethylsulfoxide (DMSO) 600 mL with stirring. The size of themaltodextrin was calculated to be in the range of 2,000 Da-4,000 Da.Once the reaction solution was complete, 1-methylimidazole (Aldrich; 2.0g, 1.9 mls) and butyric anhydride (Aldrich; 5.0 g, 5.2 mls) was addedwith stirring. The reaction mixture was stirred for four hours at roomtemperature. After this time, the reaction mixture was quenched withwater and dialyzed against DI water using 1,000 MWCO dialysis tubing.The butyrylated starch was isolated via lyophylization to give 9.315 g(85% yield). NMR confirmed a butyrylation of 1:3 B/GU (1.99 mmolesbutyl/g sample).

To provide butyrylated-MD (1:8 B/GU), 2.5 g (2.6 mL) butyric anhydridewas substituted for the amount of butyric anhydride described above. Ayield of 79% (8.741 g) was obtained. NMR confirmed a butyrylation of 1:5B/GU (1.31 mmoles butyl/g sample).

To provide butyrylated-MD (1:2B/GU), 10.0 g (10.4 mL) butyric anhydridewas substituted for the amount of butyric anhydride described above. Ayield of 96% (10.536 g) was obtained. NMR confirmed a butyrylation of1:2 B/GU (3.42 mmoles butyl/g sample).

EXAMPLE 45 Preparation of Acrylated Acylated Maltodextrin(Butyrylated-MD-Acrylate)

Preparation of an acylated maltodextrin macromer having pendent butyryland acrylate groups prepared by coupling butyric anhydride at varyingmolar ratios.

To provide butyrylated-MD-acrylate (1 butyl/4 glucose units, 1:4 B/GU)the following procedure was performed. MD-Acrylate (Example 13; 1.1 g;0.367 mmoles) was dissolved in dimethylsulfoxide (DMSO) 60 mL withstirring. Once the reaction solution was complete, 1-methylimidazole(0.20 g, 0.19 mls) and butyric anhydride (0.50 g, 0.52 mls) was addedwith stirring. The reaction mixture was stirred for four hours at roomtemperature. After this time, the reaction mixture was quenched withwater and dialyzed against DI water using 1,000 MWCO dialysis tubing.The butyrylated starch acrylate was isolated via lyophylization to give821 mg (75% yield, material lost during isolation). NMR confirmed abutyrylation of 1:3 B/GU (2.38 mmoles butyl/g sample).

EXAMPLE 46 Preparation of Acrylated Acylated Maltodextrin(Butyrylated-MD-Acrylate)

Maltodextrin having pendent butyryl and acrylate groups prepared bycoupling butyric anhydride at varying molar ratios.

To provide butyrylated-MD-acrylate the following procedure is performed.Butyrylated-MD (Example 43; 1.0 g; 0.333 mmole) is dissolved indimethylsulfoxide (DMSO) 60 mL with stirring. Once the reaction solutionis complete, a solution of EA-NCO from Example 12 (353 mg; 2.50 mmole)is evaporated and dissolved in dried DMSO 1.0 mL). The two DMSOsolutions are mixed and heated to 55⁰ C. overnight. The DMSO solution isplaced in dialysis tubing (1000 MWCO) and dialyzed against water for 3days. The macromer solution is filtered and lyophilized to give a whitesolid.

1. A medical implant comprising a biodegradable body member comprising aplurality of natural biodegradable polysaccharide associated via pendentcoupling groups, wherein the biodegradable polysaccharide has amolecular weight of 500,000 Da or less.
 2. The medical implant of claim1 wherein the natural biodegradable polysaccharide has a molecularweight of 500 Da or greater.
 3. The medical implant of claim 2 whereinthe natural biodegradable polysaccharide has a molecular weight in therange of 1000 Da to 10,000 Da.
 4. The medical implant of claim 1 whereinbiodegradable polysaccharide is selected from the group consisting ofamylose and maltodextrin.
 5. The medical implant of claim 1 whereinbiodegradable polysaccharide comprises a non-reducing naturalbiodegradable polysaccharide.
 6. The medical implant of claim 5 whereinbiodegradable polysaccharide is selected from the group consisting ofpolyalditol.
 7. The medical implant of claim 1 wherein the couplinggroup is present on the natural biodegradable polysaccharide in anamount of 0.7 mmoles or less of coupling group per milligram of naturalbiodegradable polysaccharide.
 8. The medical implant of claim 1 whereinthe coupling group is a polymerizable group.
 9. The medical implant ofclaim 8 wherein the polymerizable group is selected from vinyl groups,acrylate groups, methacrylate groups, ethacrylate groups, 2-phenylacrylate groups, acrylamide groups, methacrylamide groups, itaconategroups, and styrene groups.
 10. The medical implant of claim 9 whereinthe body member is formed by reaction of the polymerizable groups toform a crosslinked matrix of a plurality of natural biodegradablepolysaccharides, and wherein the reaction is initiated by apolymerization initiator.
 11. The medical implant of claim 10 whereinthe polymerization initiator comprises a photoinitiator comprising twoor more photoreactive groups.
 12. The medical implant of claim 10wherein the polymerization initiator comprises a redox pair.
 13. Themedical implant of claim 1 wherein the coating comprises a bioactiveagent.
 14. The medical implant of claim 13 wherein the bioactive agentis selected from the group comprising polypeptides, nucleic acids, andpolysaccharides.
 15. The medical implant of claim 14 wherein thebioactive agent has a molecular weight of 10,000 Da or greater.
 16. Themedical implant of claim 1 having a dry mass of 2.5 g or less.
 17. Themedical implant of claim 1 wherein the body member comprises a crosssection having a circular shape.
 18. The medical implant of claim 1adapted for placement into at least one portion of the eye.
 19. Themedical implant of claim 18 fabricated to have an intravitreal lifetimeof 24 hours or less.
 20. The medical implant of claim 18 fabricated tohave an intravitreal lifetime of one month or less.
 21. The medicalimplant of claim 1 wherein the body member is formed from a compositioncomprising the natural biodegradable polysaccharide at a concentrationin the range of 200 mg/mL to 2000 mg/mL.
 22. The medical implant ofclaim 1, wherein the natural biodegradable polysaccharide furthercomprise pendent hydrophobic moiety.
 23. The medical implant of claim22, wherein the pendent hydrophobic moiety comprises a fatty acid orderivative thereof.
 24. A method for delivering a bioactive agent to asubject, the method comprising the steps of: providing a medical implantto a subject, the medical implant comprising a biodegradable body membercomprising a plurality of natural biodegradable polysaccharideassociated via pendent coupling groups, wherein the biodegradablepolysaccharide has a molecular weight of 500,000 Da or less, andbioactive agent; and exposing the medical implant to a carbohydrase topromote the degradation of the medical implant and release of thebioactive agent, wherein there is substantially no release of thebioactive agent in the absence of the carbohydrase.
 25. The method ofclaim 24 wherein the bioactive agent comprises a polypeptide.
 26. Themethod of claim 25 wherein the polypeptide comprises an antibody or anantibody fragment.
 27. The method of claim 25 wherein the polypeptidehas a weight of 10 kDa or greater.
 28. The method of claim 24 wherein anamount of bioactive agent in the range of 1% to 17% of the total amountof bioactive agent present in the medical implant is released from themedical implant within a period of 8 days.
 29. The method of claim 24wherein an amount of bioactive agent in the range of 1% to 41% of thetotal amount of bioactive agent present in the medical implant isreleased from the medical implant within a period of 14 days.
 30. Themethod of claim 24 wherein an amount of bioactive agent in the range of1% to 60% of the total amount of bioactive agent present in the medicalimplant is released from the medical implant within a period of 21 days.